title: Release History

3.5.0 (2026-02-15)

Highlights

Mesa 3.5.0 is a major feature release that introduces a public event scheduling API, stabilizes the event system, and lays the groundwork for Mesa 4.0 by deprecating several legacy patterns.

Public event scheduling and time advancement

The headline feature of 3.5.0 is a new public API for event scheduling and time advancement directly on Model (#3266). Instead of interacting with experimental Simulator classes, users can now schedule events and advance time with simple, expressive methods:

# Run the model for a duration
model.run_for(10)       # Advance 10 time units
model.run_until(50.0)   # Run until absolute time 50

# Schedule one-off events
model.schedule_event(callback, at=25.0)    # At absolute time
model.schedule_event(callback, after=5.0)  # Relative to now

# Schedule recurring events
from mesa.time import Schedule
model.schedule_recurring(func, Schedule(interval=10, start=0))

For traditional ABMs, model.run_for(1) is functionally equivalent to model.step(), but this generalizes naturally to event-driven and hybrid models. The mental model shifts from "execute step N" to "advance time, and whatever is scheduled will run."

Our new Agent activation and event scheduling tutorials cover this extensively (#3280).

Stabilized event scheduling system

The event scheduling system (EventList, Event, EventGenerator, Schedule, Priority) has been moved from mesa.experimental.devs to the new stable mesa.time module (#3276), making event-based simulation a first-class feature of Mesa. The new Schedule dataclass provides a clean way to define recurring timing patterns with interval, start, end, and count parameters (#3250). See our migration guide.

Deprecations toward Mesa 4.0

This release deprecates several legacy patterns to prepare for Mesa 4.0:

Simulator classes deprecated (#3277): ABMSimulator and DEVSimulator are replaced by the new Model methods above.
seed parameter deprecated (#3147): Use the rng parameter in Model.__init__() instead.
AgentSet sequence behavior deprecated (#3208): Indexing/slicing on AgentSet is deprecated in favor of the new to_list() method.
Portrayal dictionaries deprecated (#3144): Use AgentPortrayalStyle and PropertyLayerStyle instead.

See our migration guide for more detail.

Internal architecture improvements

Under the hood, Model now uses an EventGenerator internally for step scheduling (#3260), unifying the step mechanism with the broader event system. A new _HardKeyAgentSet (#3219, #3224) replaces WeakKeyDictionary-based storage for model-managed agent collections, eliminating weak reference overhead while preventing memory leaks through automatic downgrading when creating views. An AbstractAgentSet base class (#3210) formalizes the AgentSet interface. Discrete spaces now distinguish between logical cell indices and physical spatial positions (#3268), laying the foundation for stacked spaces by adding a Cell.position property.

New agent creation from DataFrames

Agents can now be created directly from a pandas DataFrame (#3199), mapping columns to constructor arguments:

agents = MyAgent.from_dataframe(model, df)

Experimental features

Several experimental features see significant progress in this release.

Scenarios

Explicit Scenario support (#3103, #3168) provides a structured way to define and manage computational experiments separately from model logic. Scenarios encapsulate parameter sets and can be used with SolaraViz (#3178), which automatically routes slider parameters to the correct Scenario or Model and reconstructs scenarios on reset.

class MyScenario(Scenario):
    density: float = 0.7

class MyModel(Model):
    def __init__(self, width=40, scenario=None):
        super().__init__(scenario=scenario)

# 'density' is auto-detected as a Scenario parameter
page = SolaraViz(MyModel(), model_params={"width": 40, "density": Slider("Density", 0.7, 0, 1, 0.1)})

Reactive model and data collection

The Model class is now reactive (#3212): model.time is observable, and signals are emitted when agents are registered or deregistered, enabling event-driven architectures. Building on this, a new DataRecorder (#3145, #3295) provides a decoupled, event-driven data collection system that separates what to collect (DataRegistry) from when and how to store it, with memory, SQLite, Parquet, and JSON backends.

self.recorder = DataRecorder(self)
self.data_registry.track_agents(self.agents, "agent_data", "wealth").record(self.recorder)
self.data_registry.track_model(self, "model_data", "gini").record(
    self.recorder, configuration=DatasetConfig(start_time=4, interval=2)
)

Other experimental progress includes improved meta-agent support with overlapping memberships (#3172).

Note that experimental features are in active development and can have (breaking) changes in every release.

What's Changed

⏳ Deprecations

Deprecate the agent and propertylayer portrayal dicts by @EwoutH in #3144
Deprecate seed parameter in favor of rng in Model by @quaquel in #3147
Deprecate AgentSet sequence behavior and add to_list() method by @codebyNJ in #3208
Deprecate Simulator classes, add migration guide entry by @EwoutH in #3277

🎉 New features added

Add DataFrame support to Agent creation by @falloficarus22 in #3199
Add Schedule dataclass and refactor EventGenerator by @EwoutH in #3250
Add public event scheduling and time advancement methods by @EwoutH in #3266

🛠 Enhancements made

Fix: Cell.get_neighborhood() RecursionError for large radius (#3105) by @Nithin9585 in #3106
Replace PropertyDescriptor with properties by @quaquel in #3125
Ensure Cell only uses slots by @quaquel in #3121
Allow list inputs for MesaSignal observable names and signal types by @Sonu0305 in #3139
Optimise create_agents by replacing 'ListLike' approach with itertools by @codebreaker32 in #3163
Micro optimization of grid.select_random_empty_cell by @quaquel in #3214
Introduce AbstractAgentSet to agent.py and refactor AgentSet to inherit from it by @codebreaker32 in #3210
Introduce _HardKeyAgentSet in agents.py by @codebreaker32 in #3219
Refactor step scheduling to use EventGenerator internally by @EwoutH in #3260
fix: handle deprecated space_kwargs gracefully in SpaceRenderer by @DipayanDasgupta in #3269
Distinguish Logical Index from Physical Position by @codebreaker32 in #3268

🧪 Experimental features

Add explicit support for Scenarios by @quaquel in #3103
feat: Add SignalType enum for type-safe signal definitions. by @codebyNJ in #3056
Replace Computable Descriptor with @computed in mesa_signals by @codebreaker32 in #3153
Add scenario property to Agent class by @EwoutH in #3164
replace AttributeDict with a dataclass by @quaquel in #3138
Enable type-hinted Scenario subclassing and fix Model generic typing by @EwoutH in #3168
Optimise mesa_signals by skipping signals for empty subscribers to reduce subsequent overheads by @codebreaker32 in #3198
Add EventGenerator class for recurring event patterns by @EwoutH in #3201
Support multiple and overlapping meta-agent memberships by @falloficarus22 in #3172
fix: update meta_agents extract_class to use to_list() by @Jayantparashar10 in #3241
Making Model reactive by @quaquel in #3212
Add data registry by @quaquel in #3156
Add DataRecorder for reactive Data Storage and DatasetConfig for Configuration by @codebreaker32 in #3145
Support Scenarios in SolaraViz visualization by @falloficarus22 in #3178
Add DataSet.record() by @quaquel in #3295
Resolve DataRecorder off-by-one timestamp error by @codebreaker32 in #3299
Adding batch and suppress to mesa_signals by @quaquel in #3261
Only emit signal of new value of observable is different from old value by @quaquel in #3312

🐛 Bugs fixed

Fix batch_run Data Collection to Ensure Accuracy and Capture All Steps by @codebreaker32 in #3109
Fix network visualization bug: Replace array indexing with dictionary lookup by @codebyNJ in #3045
Fix TypeError in find_combinations when evaluation_func is None by @codebyNJ in #3112
Make create_meta_agent deterministic by @quaquel in #3183
Fix seed logic to ensure reproducibility by @codebreaker32 in #3192
Bugfix for pickling dynamically modified grids by @quaquel in #3217
check whether model reporter is a partial function by @wang-boyu in #3220
Prevent RecursionError and data loss in Cell/Grid deepcopy by @falloficarus22 in #3222
fix: update alliance_formation example to use AgentSet.to_list() by @souro26 in #3235
fix: preserve falsy evaluation values in find_combinations by @souro26 in #3237
Naming collision in meta-agents add_atrributes by @tpike3 in #3239
fix: update Altair tooltip type inference for compatibility by @souro26 in #3234
Fix Solara Altair dependency updates by @falloficarus22 in #3244

🔍 Examples updated

Update wolf-sheep example to use new event scheduling API by @EwoutH in #3278
Update Epstein Civil Violence model to use the new experimental Scenario class by @EwoutH in #3167

📜 Documentation improvements

Add deprecation of passing portrayal arguments to draw() methods to migration guide by @EwoutH in #3202
docs: clarify SolaraViz keyword-only model arguments by @Arjun-Sasi in #3044
docs: Add Mesa migration guide for AgentSet sequence behavior by @codebyNJ in #3218
docs: improve Boltzmann Wealth Model README structure and clarity by @souro26 in #3229
Update SpaceRenderer API in Tutorials 4, 5, and 6 by @falloficarus22 in #3231
Fix docstring in mesa_signals/core.py by @codebreaker32 in #3255
cleanup by @quaquel in #3258
Migrate tutorials and examples to model.run_for() by @falloficarus22 in #3270
Add agent activation, event scheduling and time progression tutorials by @EwoutH in #3280
Update overview.md for Mesa 3.5 by @EwoutH in #3310

🔧 Maintenance

Fix pickling for scheduled events by serializing weak-referenced callbacks safely by @EwoutH in #3205
Unify event list between Model and Simulator by @EwoutH in #3204
Fix: Replace 'assert ValueError' with proper return None by @codebyNJ in #3189
Update model.py to replace AgentSet with _HardKeyAgentSet by @codebreaker32 in #3224
Use type(model.value).init in ModelCreator param check by @falloficarus22 in #3264
Stabilize event scheduling system from experimental to mesa.time by @EwoutH in #3276
Prevent infinite loop from non-positive Schedule intervals by @souro26 in #3289

New Contributors

@champ-byte made their first contribution in #3098
@Arjun-Sasi made their first contribution in #3044
@souro26 made their first contribution in #3235
@Jayantparashar10 made their first contribution in #3241
@ApurvaPatil2401 made their first contribution in #3249

Full Changelog: https://github.com/mesa/mesa/compare/v3.4.2...v3.5.0

3.4.2 (2026-01-23)

Highlights

Mesa 3.4.2 is a bugfix release that addresses a critical memory leak affecting all Mesa models.

This release fixes a significant memory leak where model instances could never be garbage collected after agents were created (#3180). The root cause was the Agent._ids class attribute: a defaultdict that stored references to model instances to ensure unique_id values were unique per model. Because this was a class-level attribute persisting across the Python process, any model used as a key maintained a hard reference indefinitely, preventing cleanup of the model and all its associated objects even after going out of scope.

This bug had serious implications for users running multiple simulations or batch experiments, as each model instance would accumulate in RAM rather than being cleaned up, eventually exhausting available memory. The fix moves unique_id assignment from the Agent class into Model.register_agent(), with each model now maintaining its own agent_id_counter instance attribute. This eliminates persistent class-level references and allows proper garbage collection of model objects.

This release also includes a fix for PropertyLayer.from_data() to prevent unintended side effects (#3122), along with several small documentation improvements (#3104, #3124, #3127), and expanded contribution guidelines detailing Mesa's development philosophy and workflow (#3135).

What's Changed

🐛 Bugs fixed

Ensure PropertyLayer.from_data() does not have side effects by @quaquel in #3122
Fix for Memory leak by @quaquel in #3180

📜 Documentation improvements

Document Agent hashability requirement by @Sonu0305 in #3104
Fix chart_property_layers docstring by @Sonu0305 in #3124
Fix remove_property_layer docstring by @Sonu0305 in #3127
Add Mesa development process guidelines by @EwoutH in #3135

Full Changelog: https://github.com/mesa/mesa/compare/v3.4.1...v3.4.2

3.4.1 (2026-01-10)

Highlights

Mesa 3.4.1 is a patch release with bug fixes, performance improvements, and documentation enhancements. This release addresses issues affecting data collection, memory management, and grid operations while introducing performance optimizations.

This release resolves several bugs affecting simulation accuracy: fixed multiple batch_run and DataCollector issues including agenttype_reporters support (#3095), sparse data collection (#2988), and proper handling of multiple collect() calls per step (#3058); resolved MultiGrid._empty_mask not updating correctly (#3019) and infinite loops in select_random_empty_cell() (#3014); fixed a memory leak in ContinuousSpace agent removal (#3031); corrected EventList.peek_ahead() chronological ordering (#3010); and ensured FixedAgent state consistency after removal (#3100).

Several optimizations improve Mesa's performance: PropertyLayer was refactored to implement the NumPy interface directly, enabling standard NumPy syntax (#3074); select_random_empty_cell() now uses vectorized NumPy operations instead of slow O(N) Python iteration (#3087); and Cell.is_empty/is_full checks were optimized to remove unnecessary O(n) copies (#3069).

The documentation received several improvements including version warnings for visualization tutorials (#2949), updated contribution guidelines (#3028), and implementation of Vale for consistent documentation style (#3022). The entire mesa.space module is now marked as maintenance-only (#3082), with users encouraged to use mesa.discrete_space for new projects. Generic type parameters were added to Agent, AgentSet, and Model classes to improve static type checking (#2885).

We're excited to welcome 9 new contributors to Mesa in this release! Thank you to everyone who contributed bug fixes, performance improvements, and documentation enhancements.

What's Changed

🛠 Enhancements made

Optimize Cell is_empty/is_full by @codebyNJ in #3069
Refactor PropertyLayer to implement NumPy interface and deprecate wrappers by @codebreaker32 in #3074
Optimise select_random_empty_cell() in grid.py by @codebreaker32 in #3087
Add generic type parameters to Agent, AgentSet, and Model by @SiddharthBansal007 in #2885

🐛 Bugs fixed

Fix: peak_ahead returns events in correct chronological order by @Nithin9585 in #3010
fix: prevent infinite loop in select_random_empty_cell via heuristic fallback by @DipayanDasgupta in #3014
Fix: datacollector missing attribute error by @codebyNJ in #3041
Fix: Add deepcopy to agent reporters to prevent mutable reference lea… by @Nithin9585 in #3038
Add initialization check in Simulator.run_for() by @codebreaker32 in #3036
Fix: Method Reporter Validation in DataCollector by @vedantvakharia in #3002
Fix MultiGrid._empty_mask not updated correctly by @Nithin9585 in #3019
Fix: Correct data retrieval in batch_run when DataCollector.collect() called multiple times per step by @Nithin9585 in #3058
Fix: IndexError in batch_run with sparse data collection by @Nithin9585 in #2988
Fix: Add agenttype_reporters support to batch_run by @BhoomiAgrawal12 in #3095
Fix memory leak in ContinuousSpace agent removal by @Nithin9585 in #3031
Minor Refactoring in solara_viz by @codebreaker32 in #3059
Fix: Correct FixedAgent state after removal by @Sonu0305 in #3100

🔍 Examples updated

Resolve FIXME in sugarscape_g1mt/agents.py by @Sonu0305 in #3062
Update alliance formation mode by @quaquel in #3075

📜 Documentation improvements

document Model.time in Model API by @Gee307 in #3020
docs: Add example structure and policy to contributing guide by @EwoutH in #3028
Changed broken documentation link in docs/tutorials/1_adding_space.ipynb by @ShashwatAwate in #2973
Updated CONTRIBUTING.md to replace old black documentation with new ruff format. by @falloficarus22 in #3071
docs: Add Mesa 3.3+ version warnings to visualization tutorials by @Srinath0916 in #2949
Implementation of Vale by @vedantvakharia in #3022
Mark whole mesa.space module maintenance-only by @quaquel in #3082

🔧 Maintenance

CI: Restore coverage collection after test reorganization by @falloficarus22 in #3006
Fix flaky Playwright test in test_examples_viz.py by @vedantvakharia in #3039
tests: consolidate Solara viz tests and restore Altair coverage #2993 by @DipayanDasgupta in #3011
test: add coverage for ignore_missing=True in DataCollector by @disgruntled-penguin in #3054
test: ensure DataCollector raises ValueError when collecting data for… by @disgruntled-penguin in #3053
Lint: Enable RUF012 and annotate mutable class attributes with ClassVar by @falloficarus22 in #3033

New Contributors

@Gee307 made their first contribution in #3020
@DipayanDasgupta made their first contribution in #3014
@ShashwatAwate made their first contribution in #2973
@vedantvakharia made their first contribution in #3039
@codebyNJ made their first contribution in #3041
@disgruntled-penguin made their first contribution in #3054
@Sonu0305 made their first contribution in #3062
@Srinath0916 made their first contribution in #2949
@BhoomiAgrawal12 made their first contribution in #3095

Full Changelog: https://github.com/mesa/mesa/compare/v3.4.0...v3.4.1

3.4.0 (2025-12-24)

Highlights

The Mesa 3.4.0 feature release introduces universal time tracking, improves batch run reproducibility, and strengthens our deprecation policy. This release also requires Python 3.12+ and includes numerous bug fixes and quality-of-life improvements.

Universal simulation time with `model.time`

Mesa now provides a single source of truth for simulation time through the model.time attribute (#2903). Previously, time was fragmented across different components - simple models used model.steps as a proxy, while discrete event simulations stored time in simulator.time. This created complexity for features needing consistent time access.

Now all models have a model.time attribute that:

Automatically increments with each step (by 1.0)
Works seamlessly with discrete event simulators
Provides a consistent interface for data collection, visualization, and user code

# Basic usage - time auto-increments
model = Model()
model.step()
print(model.time)  # 1.0

# With discrete event simulation
simulator = DEVSimulator()
simulator.setup(model)
simulator.schedule_event_absolute(some_function, 2.5)
simulator.run_until(3.0)
print(model.time)  # 3.0

The old simulator.time still works but emits a deprecation warning.

Improved batch run reproducibility

The batch_run function has been updated to provide explicit control over random seeds across replications (#2841). Previously, using iterations with a fixed seed caused all iterations to use the same seed, producing identical results instead of independent replications.

The new rng parameter accepts either a single seed value or an iterable of seed values, giving you complete control over reproducibility:

rng = np.random.default_rng(42)
seed_values = rng.integers(0, sys.maxsize, size=(5,))

results = mesa.batch_run(
    MoneyModel,
    parameters=params,
    rng=seed_values.tolist(),  # Each iteration uses a different seed
)

The old iterations parameter is now deprecated and will be removed in Mesa 4.0. See the migration guide for details on updating your code.

Strengthened deprecation policy

Mesa now has a formal deprecation policy that ensures users have adequate time to migrate while allowing Mesa to evolve (#2900). A related change is that all deprecation warnings now use FutureWarning instead of DeprecationWarning (#2905), making them visible by default since DeprecationWarning is hidden for imported modules.

The policy guarantees:

New features must be available for at least one minor release before deprecating old ones
Documentation, migration guides, and examples must be updated before active deprecation
Breaking changes only occur in major version releases
Experimental features have more flexibility but still communicate changes

Organization name change

Mesa has migrated from the projectmesa to mesa organization on GitHub (#2880), (#2887), thanks to Daniel Langemann (@dlangemann) who generously transferred the mesa name to us. Our repositories are now accessible at github.com/mesa/mesa instead of github.com/projectmesa/mesa, signaling authority and maturity in a way that better reflects Mesa's position as the agent-based modeling framework in Python. GitHub automatically redirects old links, so existing URLs and git remotes continue to work seamlessly.

Python 3.12+ required

Mesa 3.4.0 drops support for Python 3.11 and now requires Python 3.12 or higher (#2842). This allows Mesa to use modern Python type parameter syntax and prepares the codebase for future Python features. Python 3.14 is now also fully tested in CI.

Other improvements

This release includes significant enhancements to the visualization system, including support for AgentPortrayalStyle in Altair components, improved property layer styling, and better error handling. The experimental cell space module has been removed in favor of the stable mesa.discrete_space module (#2969).

Numerous bugs were fixed, including issues with scalar color handling in matplotlib, empty cell collection indexing, and cell capacity handling. The test suite was reorganized to mirror the source module structure and now treats warnings as errors to prevent accumulation.

We welcome 10 new contributors to the Mesa project in this release! Thank you to everyone who contributed bug fixes, documentation improvements, and feature enhancements.

What's Changed

⏳ Deprecations

Replace DeprecationWarnings with FutureWarnings by @EwoutH in #2905
Fix: Auto-increment seed across batch_run iterations by @EwoutH in #2841

🎉 New features added

Add model.time as universal source of truth for simulation time by @EwoutH in #2903

🛠 Enhancements made

Refactor SpaceRenderer API to separate setup and draw methods by @Sahil-Chhoker in #2893
Validate HexGrid torus dimensions by @ShreyasN707 in #2951
Allow PropertyLayerStyle instance in draw_propertylayer by @ShreyasN707 in #2936
Support AgentPortrayalStyle in Altair visualization components by @EwoutH in #2985

🐛 Bugs fixed

Update visualization tabs to be compatible with ipyvuetify 3.0 by @EwoutH in #2919
Use pandas type checking for numeric dtype detection in Altair backend by @EwoutH in #2917
Fix for Model.reset_rng by @quaquel in #2946
Fix scalar color handling in legacy matplotlib backend. by @falloficarus22 in #2959
Fix: IndexError in select_random_agent when cell collection is empty by @Nithurshen in #2983
Fix: Handle capacity=None in Cell.is_full property by @Nithin9585 in #2981
Fix/cell capacity zero by @ahmednabiled in #2990
Fix SolaraViz multipage rendering when renderer is absent by @falloficarus22 in #2966

🔍 Examples updated

examples: Add Activation Order and Grid Type selectors to EpsteinCivilViolence by @Nithurshen in #2955

📜 Documentation improvements

Docs: Link to online example model demo in a few places by @EwoutH in #2882
Update overview.md by @quaquel in #2883
docs: Changed colab notebook url for tutorial 3 - agentset by @aten2005 in #2890
Add AI/LLM use guidelines to Code of Conduct by @EwoutH in #2898
docs: Add deprecation policy to contributor guide by @EwoutH in #2900
[Docs] Fix typos and inconsistent comments in tutorials by @Mannan-15 in #2948
Remove capacity constraint on cells from tutorial by @quaquel in #2964
Fix Navigation Issue by @codebreaker32 in #2938

🔧 Maintenance

Drop Python 3.11, require Python 3.12+ and update to modern type parameter syntax by @EwoutH in #2842
Pin Readthedocs build to Python 3.13 by @EwoutH in #2899
tests: Resolved "Missing Random Number Generator" warnings by @ShreyasN707 in #2911
tests: Update agent portrayals to use AgentPortrayalStyle by @Tejasv-Singh in #2909
Add Python 3.14 support to workflows and metadata by @EwoutH in #2843
Fix dtype/default_value mismatches in PropertyLayer tests to resolve UserWarnings by @ShreyasN707 in #2913
Replace deprecated np.bmat with np.block in Voronoi Delaunay triangulation by @EwoutH in #2915
Speed up CI by installing only Playwright chromium-headless-shell by @EwoutH in #2916
Add deprecation category to release notes by @EwoutH in #2914
test: Update simulator.time deprecation test to expect FutureWarning by @EwoutH in #2922
tests: Migrate PropertyLayer portrayals from dict to PropertyLayerStyle by @Tejasv-Singh in #2920
Fix matplotlib figure memory leak warning in tests by @EwoutH in #2924
Update organization name from projectmesa to mesa by @EwoutH in #2880
Update dict-based agent portrayals to use AgentPortrayalStyle in tests by @falloficarus22 in #2934
Remove experimental cell_space module and update references by @EwoutH in #2969
Fix PropertyLayer default value type mismatch warnings by @falloficarus22 in #2963
test: Replace deprecated iterations with rng in batch_run tests by @EwoutH in #2984
End of year cleanup by @EwoutH in #2971
Reorganize tests to mirror source module structure by @EwoutH in #2994
SolaraViz: move hooks before early return in ComponentsView by @EwoutH in #2925
Fix reproducibility warnings by adding explicit random parameters by @codebreaker32 in #2978
ci: treat warnings as errors to prevent accumulation by @EwoutH in #2926
Reject negative time_delta in schedule_event_relative by @Nithin9585 in #2999
CI: Add job that runs tests with pip pre-release dependencies by @EwoutH in #1852
CI: Split off separate coverage job by @EwoutH in #3005
Model: remove unreleased step_duration parameter by @EwoutH in #3007

New Contributors

@GlyphicGuy made their first contribution in #2892
@aten2005 made their first contribution in #2890
@Tejasv-Singh made their first contribution in #2908
@ShreyasN707 made their first contribution in #2911
@Mannan-15 made their first contribution in #2948
@falloficarus22 made their first contribution in #2959
@codebreaker32 made their first contribution in #2938
@Nithurshen made their first contribution in #2955
@Nithin9585 made their first contribution in #2981
@ahmednabiled made their first contribution in #2990

Full Changelog: https://github.com/mesa/mesa/compare/v3.3.1...v3.4.0

3.3.1 (2025-11-07)

Highlights

Mesa 3.3.1 is a maintenance release focused on bug fixes and documentation improvements following the major 3.3.0 visualization update.

This release addresses two critical visualization bugs affecting PropertyLayers on HexGrids and property layer data mapping across both Altair and Matplotlib backends.

The documentation received several important updates, including fixes to tutorial code examples, a new guide for Google Summer of Code contributors, and improved organization of the documentation structure. The migration guide has been updated to reflect the deprecation of the old agent_portrayal parameter in favor of the new AgentPortrayalStyle introduced in Mesa 3.3.0.

We're excited to welcome six new contributors to the Mesa project in this release! Thank you to everyone who contributed bug fixes, documentation improvements, and test coverage enhancements.

What's Changed

🐛 Bugs fixed

Fix visualization error for PropertyLayers on HexGrids. Add transpose … by @flucco in mesa#2868
Fix: Property layer data mapping for both Altair and Matplotlib backends by @Sahil-Chhoker in mesa#2869
Fix: AgentSet initialization should not require explicit random number generator by @verisimilidude2 in mesa#2789

🔍 Examples updated

Fix missing variable g in the tutorial by @pazmiller in mesa#2849

📜 Documentation improvements

fix broken link in example by @BigTurtle8 in mesa#2847
Docs: Fix ValueError in tutorial by adding default value to MoneyModel by @pragam-m25 in mesa#2871
Add guide for GSoC contributors by @colinfrisch in mesa#2873
Deprecate agent_portrayal and update Migration guide by @Sahil-Chhoker in mesa#2872
Docs: List overview separate from tutorials by @dhiraj-143r in mesa#2878

🔧 Maintenance

ruff fixes in visualization by @quaquel in mesa#2867
[pre-commit.ci] pre-commit autoupdate: Update to ruff v0.13 by @pre-commit-ci[bot] in mesa#2840
Tests: Add test for InputText in UserInputs by @pragam-m25 in mesa#2870

New Contributors

@BigTurtle8 made their first contribution in mesa#2847
@pazmiller made their first contribution in mesa#2849
@flucco made their first contribution in mesa#2868
@pragam-m25 made their first contribution in mesa#2870
@dhiraj-143r made their first contribution in mesa#2878
@verisimilidude2 made their first contribution in mesa#2789

Full Changelog: https://github.com/mesa/mesa/compare/v3.3.0...v3.3.1

3.3.0 (2025-09-06)

Highlights

The major highlight of release 3.3.0 is the introduction of a new and improved visualization module. This effort was @Sahil-Chhoker's Google Summer of Code project . The new module is backwards compatible and continues to use Solara. It has several new and improved features to include:

AgentPortrayalStyle: a more user-friendly way to specify agent portrayal
PropertyLayerStyle: Makes property_layer and agent portrayal consistent.
SpaceRender: a new component for drawing spaces, agents and property layers with extensive customization
Improved support for Altair and Matplotlib
Multipage support (e.g., users can display simulation on one page and charts of the model on another)
Updated tutorials for visualization

You can read more about the update here

In addition, there were many other improvements to mesa, from bug fixes to improved CI/CD pipelines. Thanks to the PyCON sprints and the developers who supported Mesa!

What's Changed

🧪 Experimental features

Introduction of Space Renderer by @Sahil-Chhoker in mesa#2803

🎉 New features added

docs/nix flake by @hussainsultan in mesa#2788

🛠 Enhancements made

Added AgentPortrayalStyle and PropertyLayerStyle by @Sahil-Chhoker in mesa#2786
Allow image markers to plot agents by @Holzhauer in mesa#2799
Renderer null check fix in solaraviz by @Sahil-Chhoker in mesa#2809
Add Altair plotting functionality by @Sahil-Chhoker in mesa#2810
Fix: Grid not showing in altair if both draw_structure and draw_agents are called. by @Sahil-Chhoker in mesa#2817
Allowing color mapping to integers in AgentPortrayalStyle by @Sahil-Chhoker in mesa#2818
Added multipage functionality by @Sahil-Chhoker in mesa#2827

🐛 Bugs fixed

Bugfix ModelCreator for required model parameters and user adjusted model parameters by @Holzhauer in mesa#2780
Remove unneeded int cast by @derkweijers in mesa#2791
Add quotes to readme to insure multi-terminal compliance. by @jackiekazil in mesa#2787
Fix broken docs link - Fix issue 2792 by @catherinedevlin in mesa#2793
Bug fixes for portrayal components by @Sahil-Chhoker in mesa#2798
fix : prevent breakdown when citizen_density (Initial Agent Density s… by @colinfrisch in mesa#2806
Fix issue #2812 by @Tosiekdev in mesa#2821

📜 Documentation improvements

Benchmarks documentation by @colinfrisch in mesa#2764
minor corrections in tutorials by @Holzhauer in mesa#2778
Correct example code in "Overview of the MESA library" by @Holzhauer in mesa#2781
Updating Examples and Docs inline with the new API. by @Sahil-Chhoker in mesa#2819

🔧 Maintenance

Add .coderabbit.yaml file to allow reviewing and updating our CodeRabbit configuration by @EwoutH in mesa#2761
add nix flake by @hussainsultan in mesa#2785
Removing Deprecations Warnings from agent_portrayal and propertylayer_portrayal until next release. by @Sahil-Chhoker in mesa#2797
Added Basic Visualization tests by @Sahil-Chhoker in mesa#2767

Other changes

Update init.py by @tpike3 in mesa#2770
[pre-commit.ci] pre-commit autoupdate by @pre-commit-ci[bot] in mesa#2751
[pre-commit.ci] pre-commit autoupdate by @pre-commit-ci[bot] in mesa#2802
[pre-commit.ci] pre-commit autoupdate by @pre-commit-ci[bot] in mesa#2808
Bump actions/download-artifact from 4 to 5 by @dependabot[bot] in mesa#2826
Bump actions/checkout from 4 to 5 by @dependabot[bot] in mesa#2825
[pre-commit.ci] pre-commit autoupdate by @pre-commit-ci[bot] in mesa#2823

New Contributors

@derkweijers made their first contribution in mesa#2791
@hussainsultan made their first contribution in mesa#2785
@catherinedevlin made their first contribution in mesa#2793
@Tosiekdev made their first contribution in mesa#2821

Full Changelog: https://github.com/mesa/mesa/compare/v3.2.0...v3.3.0

3.2.0 (2025-05-04)

Highlights

Mesa 3.2.0 is a feature-packed release, which stabilizes our discrete space, improves many of our visualisation capabilities, improves our tutorial organization, adds the experimental meta-agents, and includes other quality of life enhancements.

We also celebrate the publication of our peer-reviewed Mesa 3 paper in JOSS. See the updated Citing Mesa section on how to cite us.

Stabilization of Discrete Space

The experimental Cell Space system has been stabilized and is now available as mesa.discrete_space (#2610). This powerful spatial modeling framework enables cell-centric simulations with integrated PropertyLayers and improved agent movement capabilities. Key improvements include:

Support for dynamic modifications to discrete spaces during simulation (#2755)
Methods to add/remove cells and connections in real-time
Full integration with PropertyLayers (#2440) for representing environmental variables
Compatible with all examples and existing visualizations

The PropertyLayer itself has also been stabilized, allowing for efficient management of spatial environmental properties like terrain, resources, or any grid-based variables. Core examples including Schelling, Game of Life, Boltzmann Wealth, and Virus on Network have been updated to use the new discrete space system.

Enhanced Visualization Experience

The SolaraViz visualization system has received substantial upgrades:

Command Console (#2697): An interactive Python console embedded directly in the visualization, allowing real-time model inspection and manipulation
Asynchronous Updates (#2656): Visualization now runs in a separate thread, dramatically improving performance for complex models
Dark Mode (#2689): Support for Solara Dark theme, automatically matching system preferences
Improved Error Handling (#2747, #2753): Better visualization of errors with options to view detailed traceback information
Enhanced UI: Arrow key navigation (#2725), movable input field with auto-scroll (#2710), and other quality-of-life improvements
PropertyLayer visualisation in Altair (#2643): Support for visualising PropertyLayers using the Altair frontend in Solara.

Restructured and updated tutorial

Our introduction tutorial has been completely restructured (#2731). Instead of one huge notebook, the tutorial is now divided into smaller, focused modules that build progressively:

Creating Your First Model: Essential basics to get started
Adding Space: Learn how to use the new discrete space system
Collecting Data: Effectively gather model statistics
AgentSet: Master agent management techniques
Visualization: Series of modules covering basic to advanced visualization

Introducing Meta-Agents

Complex systems often have multiple levels of components. An organization is not one entity, but is made of departments, sub-departments, and people. A person is not a single entity, but it is made of micro biomes, organs and cells. A city is not a single entity, but it is made of districts, neighborhoods, buildings, and people. A forest comprises an ecosystem of trees, plants, animals, and microorganisms.

This reality is the motivation for meta-agents. It allows users to represent these multiple levels, where each level can have meta-agents with constituting agents.

Meta agents #2748

To demonstrate meta-agents capability there are two examples:

Dynamic meta-agent creation - Alliance formation, which shows emergent meta-agent formation through a game theoretic based alliance formation.
Deliberate meta-agent creation - Warehouse model, which provides a pseudo warehouse model to demonstrate meta-agent functionality.

Let us know what you think on our Matrix Channel

Other improvements

AgentSet's agg method now supports multiple aggregation functions in a single call (#2743)
Many documentation improvements have been made based on feedback by our JOSS reviewers

What's Changed

🎉 New features added

Stabilize experimental Cell Space as mesa.discrete_space by @quaquel in mesa#2610
Feat: Added Command Console by @Sahil-Chhoker in mesa#2697
Stabilize PropertyLayer by @EwoutH in mesa#2440

🛠 Enhancements made

Visualisation: Add dark mode by @sanika-n in mesa#2689
Creating threads to update visualization asynchronously by @HMNS19 in mesa#2656
Movable Input Field with auto-scroll by @Sahil-Chhoker in mesa#2710
Feat: Added arrow key navigation by @Sahil-Chhoker in mesa#2725
added property_layer with altair by @sanika-n in mesa#2643
Debug option for errors in visualisation by @colinfrisch in mesa#2747
Debug option for errors in visualisation front end by @colinfrisch in mesa#2753
Add support for dynamic discrete spaces by @quaquel in mesa#2755
Support multiple functions in AgentSet agg method by @EwoutH in mesa#2743

🔍 Examples updated

Move boltzmann to cell spaces by @quaquel in mesa#2680
Move Game of life to cell space by @quaquel in mesa#2681
Move Schelling to discrete space by @quaquel in mesa#2684
Move virus_on_a_network to discrete_space by @quaquel in mesa#2688
Update boid_flockers example include flight direction by @sanika-n in mesa#2696

📜 Documentation improvements

docs: Split off the overview page, extend with spaces/activation by @EwoutH in mesa#2673
docs: Add Roles section to CONTRIBUTING.md by @EwoutH in mesa#2694
[JOSS] Docs: Clarify difference between core and user examples by @EwoutH in mesa#2706
[JOSS] docs: Improve batch_run documentation for parallel processing by @EwoutH in mesa#2707
JOSS Tutorial Fixes by @tpike3 in mesa#2708
Clean-up old images, compress wolf-sheep image, remove version switch artifact by @EwoutH in mesa#2717
docs: Update citation to JOSS article by @EwoutH in mesa#2740
update intro tutorial discrete space by @tpike3 in mesa#2731
docs: fix broken links to Readthedocs in example descriptions by @reyan-singh in mesa#2757

🧪 Experimental features

Meta agents by @tpike3 in mesa#2748

🐛 Bugs fixed

Minor (bug) fixes to discrete_space by @quaquel in mesa#2687
Fixed Marker in mpl by @sanika-n in mesa#2670

New Contributors

@colinfrisch made their first contribution in mesa#2747
@reyan-singh made their first contribution in mesa#2757

Full Changelog: https://github.com/mesa/mesa/compare/v3.1.4...v3.2.0

3.1.5 (2025-03-26)

Highlights

Mesa 3.1.5 is a maintenance release focused on improving documentation and cleaning up our resources. This update includes no breaking changes and is compatible with previous 3.1.x releases.

The documentation improvements include enhanced explanations for batch run parallel processing, a significantly expanded overview section covering spaces, property layers and time advancement methods with practical code examples, and a clearer installation guide detailing what the optional [rec] dependencies provide. We've also improved our examples documentation to better distinguish between core and user-contributed examples, and added a new "Roles" section to the contributing guide that outlines the project's community structure and progression paths.

On the maintenance side, we've cleaned up unused images and compressed existing ones, reducing the repository size by over 2MB and distribution size from 3.2MB to 1.2MB.

What's Changed

📜 Documentation improvements

docs: Split off the overview page, extend with spaces/activation by @EwoutH in mesa#2673
docs: Add Roles section to CONTRIBUTING.md by @EwoutH in mesa#2694
[JOSS] Docs: Clarify difference between core and user examples by @EwoutH in mesa#2706
[JOSS] docs: Improve batch_run documentation for parallel processing by @EwoutH in mesa#2707
Clean-up old images, compress wolf-sheep image, remove version switch artifact by @EwoutH in mesa#2717

Full Changelog: https://github.com/mesa/mesa/compare/v3.1.4...v3.1.5

3.1.4 (2025-02-09)

Highlights

This release contains various improvements and bugfixes to the matplotlib-based visualization of spaces. Hexgrids are now fully supported, including property layers. In making this possible, various minor bugs were encountered and also fixed. In addition to the visualization improvements, there are various minor convenience improvements to the docs.

What's Changed

🛠 Enhancements made

Fixed hex-space draw function to avoid overlaps by @Sahil-Chhoker in mesa#2609
Fix: Property layer visualization for HexGrid by @Sahil-Chhoker in mesa#2646
Enhance DataCollector to validate model_reporters functions by @peter-kinger in mesa#2605
Implemented post_process in Altair based components by @sanika-n in mesa#2641

🐛 Bugs fixed

bugfix for draw_property_layer by @quaquel in mesa#2639
Uses array for hex grid property layer fix by @Sahil-Chhoker in mesa#2651
Update Binder environment to use latest Mesa version (#2652) by @aarav-shukla07 in mesa#2655
Change Hexgrid._connect_cells_2d to use x,y coordinates by @quaquel in mesa#2632

🔍 Examples updated

Added property layer viz to sugarscape by @sanika-n in mesa#2653
added color-bar for spice by @sanika-n in mesa#2622

📜 Documentation improvements

remove any reference to using --pre by @quaquel in mesa#2618
Updated Docs by @sanika-n in mesa#2624
Fixed 404 error for Examples Tab in Introductory Tutorial (#2662) by @aarav-shukla07 in mesa#2664
Documentation by @Spartan-71 in mesa#2630
Adding a copy option at the top of the code written in the docs by @PrashantChoudhary13579 in mesa#2628
Adding Mesa Extension page by @PrashantChoudhary13579 in mesa#2627

🔧 Maintenance

remove remnants of mesa cli by @quaquel in mesa#2617
benchmarks.yml: Install SciPy and use uv for pip install by @EwoutH in mesa#2633
[pre-commit.ci] pre-commit autoupdate by @pre-commit-ci in mesa#2659

New Contributors

@PrashantChoudhary13579 made their first contribution in mesa#2628
@aarav-shukla07 made their first contribution in mesa#2655
@peter-kinger made their first contribution in mesa#2605

Full Changelog: https://github.com/mesa/mesa/compare/v3.1.3...v3.1.4

3.1.3 (2025-01-11)

Highlights

Mesa 3.1.3 introduces a major experimental reimplementation of Mesa's continuous space, providing an intuitive agent-centric API and significant performance improvements. The new implementation supports n-dimensional spaces and offers streamlined methods for agent movement and neighbor calculations.

New Continuous Space Features

Agent-centric movement API similar to cell spaces
Efficient neighbor calculations and position updates
Support for n-dimensional spaces
Improved memory management with dynamic array resizing

Here's a quick look at the new API:

# Create a 2D continuous space
space = ContinuousSpace(
    dimensions=[[0, 1], [0, 1]],
    torus=True,
    random=model.random
)

# Create and position an agent
agent = ContinuousSpaceAgent(space, model)
agent.position = [0.5, 0.5]

# Move agent using vector arithmetic
agent.position += [0.1, 0.1]

# Get neighbors within radius
neighbors, distances = agent.get_neighbors_in_radius(radius=0.2)

# Find k nearest neighbors
nearest, distances = agent.get_nearest_neighbors(k=5)

The new implementation particularly benefits models requiring frequent position updates and neighbor queries, such as flocking simulations or particle systems. See #2584 for more details. We would love to get feedback on the new Continuous Space in #2611.

Other improvements in this release include consistent visualization behavior across space types with the reimplementation of draw_voronoi #2608, and a new render interval slider for controlling visualization update frequency in SolaraViz, which helps improve performance when working with complex visualizations #2596. We've also fixed a bug affecting random number generation determinism when using Model(seed=something), ensuring both model.random and model.rng now behave consistently when seeded with the same initial value #2598.

What's Changed

🧪 Experimental features

Reimplementation of Continuous Space by @quaquel in mesa#2584

🛠 Enhancements made

reimplementation of draw_voroinoi by @quaquel in mesa#2608
Add render interval slider to control visualization update frequency by @HMNS19 in mesa#2596

🐛 Bugs fixed

Bugfix for non deterministic rng behavior by @quaquel in mesa#2598

🔍 Examples updated

Clarify ContinuousSpace.get_neighbors behavior with multiple agents at same position by @quaquel in mesa#2599

New Contributors

@HMNS19 made their first contribution in mesa#2596

Full Changelog: https://github.com/mesa/mesa/compare/v3.1.2...v3.1.3

3.1.2 (2025-01-04)

Highlights

Mesa v3.1.2 is a patch release containing updates to our wolf-sheep, shelling and prisoner's dilemma example models and improving documentation in the tutorials and visualisation docstring. No functional changes to the core library were made.

What's Changed

🔍 Examples updated

examples/wolf_sheep: Don't allow dumb moves by @EwoutH in mesa#2503
Added homophily ratio in basic schelling example by @vbv-shm in mesa#2520
examples: Update pd_grid analysis.ipynb to use new spaces by @quaquel in mesa#2553

📜 Documentation improvements

Corrected a few errors in Intro tutorial by @sanika-n in mesa#2583
Small draw_space docstring fix by @quaquel in mesa#2554
fix: model name in visualization tutorial by @Sahil-Chhoker in mesa#2591

New Contributors

@vbv-shm made their first contribution in mesa#2520
@sanika-n made their first contribution in mesa#2583

Full Changelog: https://github.com/mesa/mesa/compare/v3.1.1...v3.1.2

3.1.1 (2024-12-14)

Highlights

Mesa 3.1.1 is a maintenance release that includes visualization improvements and documentation updates. The key enhancement is the addition of an interactive play interval control to the visualization interface, allowing users to dynamically adjust simulation speed between 1ms and 500ms through a slider in the Controls panel.

Several example models were updated to use Mesa 3.1's recommended practices, particularly the create_agents() method for more efficient agent creation and NumPy's rng.integers() for random number generation. The Sugarscape example was modernized to use PropertyLayers.

Bug fixes include improvements to PropertyLayer visualization and a correction to the Schelling model's neighbor similarity calculation. The tutorials were also updated to reflect current best practices in Mesa 3.1.

What's Changed

🎉 New features added

Add Interactive Play Interval Control to Mesa Visualization by @AdamZh0u in mesa#2540

🐛 Bugs fixed

bug fixes for draw_property_layers by @quaquel in mesa#2548

🔍 Examples updated

Wolf-sheep to use create_agent by @quaquel in mesa#2543
Shift sugarscape example to using create_agent by @quaquel in mesa#2544
Fix: Schelling Model Neighbor Similarity Calculation by @Sahil-Chhoker in mesa#2518
Change pd_grid example to use create_agents by @quaquel in mesa#2545
Switch sugarscape to using property layers by @quaquel in mesa#2546

📜 Documentation improvements

Updated docs and check_model param by @nissu99 in mesa#2510
Update tutorials to use create_agents and rng.integers by @DarshPareek in mesa#2541

New Contributors

@nissu99 made their first contribution in mesa#2510
@DarshPareek made their first contribution in mesa#2541

Full Changelog: https://github.com/mesa/mesa/compare/v3.1.0...3.1.1

3.1.0 (2024-12-04)

Highlights

With Mesa 3.1.0 we're back on our regular release schedule after the big Mesa 3.0 release, with some exciting new features.

This release adds experimental support for Observables and Computed, enabling a more reactive and responsive programming model for agent-based simulations. The new Observable and Computable classes allow developers to declaratively define attributes that automatically emit signals when their values change, and compute derived values that update dynamically. This lays the groundwork for more advanced event handling and data visualization features in future releases (#2291).

The experimental cell space module has been updated with full support for n-dimensional property layers. These allow agents to easily interact with and modify spatial properties of the environment, such as terrain, resources, or environmental conditions. The new implementation provides a more intuitive attribute-based API and ensures tight integration with the cell space architecture (#2512).

Mesa now includes built-in support for logging using the standard Python logging module. This provides developers with a flexible and powerful way to add structured diagnostic and debug output to their simulations, without the need for custom logging solutions. The logging system is integrated throughout the library, including the new SolaraViz visualization system (#2506).

Creating multiple agents with varying initialization parameters is now significantly easier with the new Agent.create_agents class method. This factory function supports both uniform and per-agent parameters, simplifying the code required to set up a simulation with a large number of heterogeneous agents (#2351).

In addition to the major new features, this release includes a number of smaller enhancements and bug fixes that improve the overall developer experience. These include removing deprecated functionality, cleaning up examples, and addressing various edge cases reported by the community. Mesa 3.1 requires Python 3.11 or higher.

What's Changed

🧪 Experimental features

Add support for Observables to MESA by @quaquel in mesa#2291
Add full support for property layers to cell spaces by @quaquel in mesa#2512

🎉 New features added

Add logging to MESA by @quaquel in mesa#2506
Add create_agents factory method to Agent by @quaquel in mesa#2351

🔍 Examples updated

Add seed control to all examples by @quaquel in mesa#2496

📜 Documentation improvements

doc fix for pip install error on mac by @quaquel in mesa#2508
Refactored docs for Introductory Tutorial by @Spartan-71 in mesa#2511
Add module-level docstring to experimental features by @EwoutH in mesa#2532

🔧 Maintenance

Remove deprecated time module by @EwoutH in mesa#2476
Drop support for Python 3.10, require Python >= 3.11 by @EwoutH in mesa#2474
Remove deprecated functionality by @EwoutH in mesa#2483
Remove visualization modules from mesa.experimental by @quaquel in mesa#2495
Cleanup two occurrences of removed scheduler by @EwoutH in mesa#2499
move _setup_agent_registration into Model.__init__ by @quaquel in mesa#2501
remove devs related examples from devs/examples by @quaquel in mesa#2507
added empty iterable checks and updated tests by @Sahil-Chhoker in mesa#2523
Fix: running Mesa in Docker with Schelling model by @AdamZh0u in mesa#2524

New Contributors

@Spartan-71 made their first contribution in mesa#2511
@Sahil-Chhoker made their first contribution in mesa#2523
@AdamZh0u made their first contribution in mesa#2524

Full Changelog: https://github.com/mesa/mesa/compare/v3.0.3...v3.1.0

3.0.3 (2024-11-14)

Highlights

A small bugfix release that fixes two bugs.

What's Changed

🧪 Experimental features

cell_space: Allow CellCollection to be empty by @EwoutH in mesa#2502

🐛 Bugs fixed

Only set model_parameters once by @Corvince in mesa#2505

Full Changelog: https://github.com/mesa/mesa/compare/v3.0.2...v3.0.3

3.0.2 (2024-11-11)

Highlights

Mesa 3.0.2 is a small follow-up patch release, in which we fixed a lot of small bugs in the example models their visualisation, and improved their testing.

What's Changed

🐛 Bugs fixed

allow components as a positional argument again by @Corvince in mesa#2488

🔍 Examples updated

examples: Add required components keyword by @EwoutH in mesa#2485
examples: Fix boid_flockers viz by @EwoutH in mesa#2492
examples: Fix schelling viz by @EwoutH in mesa#2490
example: Add input sliders to Sugarscape viz by @EwoutH in mesa#2487
examples/gol: Add initial fraction alive, add sliders to viz by @EwoutH in mesa#2489

🔧 Maintenance

test app init of examples by @Corvince in mesa#2491

Full Changelog: https://github.com/mesa/mesa/compare/v3.0.1...v3.0.2

3.0.1 (2024-11-11)

Highlights

After our huge 3.0.0 release, Mesa 3.0.1 follows up with two improvements to experimental features, examples and docs.

What's Changed

🧪 Experimental features

Bugfixes to DEVS by @quaquel in mesa#2478
Support simulators in SolaraViz by @quaquel in mesa#2470

🛠 Enhancements made

issue a user warning if random is None by @quaquel in mesa#2479

🔍 Examples updated

Integrate benchmarks and example models by @EwoutH in mesa#2473

📜 Documentation improvements

docs/tutorial: Replace scheduler in MoneyModel by @EwoutH in mesa#2475
docs: update migration_guide.md by @eltociear in mesa#2480
Update some DeprecationWarnings to note they are removed in Mesa 3.1 by @EwoutH in mesa#2481

New Contributors

@eltociear made their first contribution in mesa#2480

Full Changelog: https://github.com/mesa/mesa/compare/v3.0.0...v3.0.1

3.0.0 (2024-11-09)

Highlights

Mesa 3.0 brings major improvements to agent-based modeling, making it more intuitive and powerful while reducing complexity. This release modernizes core functionalities and introduces new capabilities for both beginners and advanced users.

Streamlined agent management

The centerpiece of Mesa 3.0 is its new agent management system. Agents are now automatically tracked and assigned unique IDs, eliminating common boilerplate code. The new AgentSet functionality provides an elegant and flexible way to work with agents, for example:

# Find agents meeting specific criteria
wealthy_agents = model.agents.select(lambda a: a.wealth > 1000)

# Group and analyze agents
grouped = model.agents.groupby("state")
state_stats = grouped.agg({
     "count": len,
     "avg_age": ("age", np.mean),
     "total_wealth": ("wealth", sum)
 })

# Activate agents in different patterns
model.agents.shuffle_do("step")  # Random activation
model.agents.select(lambda a: a.energy > 0).do("move")  # Conditional activation

The AgentSet provides powerful methods for filtering, grouping, and analyzing agents, making it easier to express complex model logic. Each model automatically maintains an AgentSet containing all agents (model.agents) and separate AgentSets for each agent type (model.agents_by_type). See the full AgentSet docs here.

Modern Visualization with SolaraViz

Mesa 3.0's new experimental visualization system, SolaraViz, provides a modern, interactive interface for model exploration:

from mesa.visualization import SolaraViz, make_space_component, make_plot_component

visualization = SolaraViz(
    model,
    [
        make_space_component(agent_portrayal),
        make_plot_component(["population", "average_wealth"]),
        lambda m: f"Step {m.steps}: {len(m.agents)} agents"  # Custom text component
    ],
    model_params=parameter_controls
)

Key visualization features:

Interactive browser-based interface with real-time updates
Support for both grid-based and network models
Visualization of PropertyLayers and hexagonal grids
Custom components using Matplotlib or text
Improved performance and responsiveness

Check out the Visualization Tutorial to get started.

Note: SolaraViz is in active development. We might make API breaking changes between Mesa 3.0 and 3.1.

Enhanced data collection

The DataCollector now supports collecting different metrics for different agent types, using agenttype_reporters:

self.datacollector = DataCollector(
    model_reporters={"total_wealth": lambda m: m.agents.agg("wealth", sum)},
    agent_reporters={"age": "age", "wealth": "wealth"},
    agenttype_reporters={
        Predator: {"kills": "kills_count"},
        Prey: {"distance_fled": "total_flight_distance"}
    }
)

Experimental features

Mesa 3.0 introduces several experimental features for advanced modeling:

Cell Space with integrated PropertyLayers and improved agent movement capabilities
Voronoi grid implementation
Event-scheduling simulation capabilities

These experimental features are in active development and might break API between releases.

Breaking changes

See our Mesa 3.0 migration guide for a full overview.

If you want to move existing models from Mesa 2.x to 3.0, there are a few things you have to change.

Models must explicitly initialize the Mesa base class:

class MyModel(mesa.Model):
    def __init__(self, n_agents, seed=None):
        super().__init__(seed=seed)  # Required in Mesa 3.0

Agents are created without manual ID assignment:

# Old
agent = MyAgent(unique_id=1, model=self)
# New
agent = MyAgent(model=self)

Scheduler replacement with AgentSet operations:

# Old (RandomActivation)
self.schedule = RandomActivation(self)
self.schedule.step()

# New
self.agents.shuffle_do("step")

# Old (SimultaneousActivation)
self.schedule = SimultaneousActivation(self)
self.schedule.step()

# New
self.agents.do("step")
self.agents.do("advance")

Furthermore:

Steps counter automatically increments
mesa.flat namespace removed
Python 3.10+ required
Reserved model variables (agents, steps, etc.) protected
Simplified DataCollector initialization
Old visualization system replaced by SolaraViz

Getting Started

Install Mesa 3.0:

pip install --upgrade mesa

If building a new model, we recommend checking out the updated Mesa Overview and Introductory Tutorial.

For updating existing models, we recommend upgrading in steps:

Update to latest Mesa 2.x
Address deprecation warnings
Upgrade to Mesa 3.0
Replace schedulers with AgentSet functionality

A detailed migration guide is available to help moving to Mesa 3.0. For questions or support, join our GitHub Discussions or Matrix Chat.

We would love to hear what you think about Mesa 3.0! Say hello here and leave any feedback on 3.0 here.

3.0.0rc0 (2024-11-06)

Highlights

We're releasing the Mesa 3.0 Release Candidate, ready for final testing before we release Mesa 3.0 later this week!

In this last 3.0 pre-release, the visualisation has been thoroughly updated, with a brand new API. Visualizing the experimental Cell Space, including PropertyLayers and hexagonal grids, is now also supported.

We're still working very active on the visualisation, so we have marked that experimental for Mesa 3.0. We will stabilize SolaraViz in Mesa 3.1.

Any feedback and last-minute bug reports are welcome here.

What's Changed

⚠️ Breaking changes

Viz: Refactor Matplotlib plotting by @quaquel in mesa#2430
api reorganization by @quaquel in mesa#2447

🧪 Experimental features

Mark SolaraViz as experimental for Mesa 3.0 by @EwoutH in mesa#2459

🛠 Enhancements made

expand ax.scatter kwargs that can be used by @quaquel in mesa#2445

🐛 Bugs fixed

Fix #2452 - handle solara viz model params better by @Corvince in mesa#2454
Update MoneyModel.py by @quaquel in mesa#2458

🔍 Examples updated

Updates to Epstein example by @quaquel in mesa#2429
Update examples to use updated space drawing by @quaquel in mesa#2442

📜 Documentation improvements

Update wolf-sheep png and fix typo in file name by @quaquel in mesa#2444
Include main examples readme in docs by @quaquel in mesa#2448
remove how-to guide and update docs in places by @quaquel in mesa#2449

🔧 Maintenance

remove deprecated HexGrid class by @quaquel in mesa#2441
rename make_plot_measure to make_plot_component and add some kwargs by @quaquel in mesa#2446

Full Changelog: https://github.com/mesa/mesa/compare/v3.0.0b2...v3.0.0rc0

3.0.0b2 (2024-10-26)

Highlights

Mesa 3.0 beta 2 includes major work on the example models, docs, a new tutorial and visualisation.

The included example models are now part of the Mesa package itself and directly importable, using:

from mesa.examples import BoidFlockers, BoltzmannWealthModel, ConwaysGameOfLife, ...

The advanced examples were also restructured and cleaned up.

The tutorial was completely rewritten for Mesa 3.0, including it's latest features and practices. Many of our other docs also received some love, and almost everything is now ready for Mesa 3.0.

A new feature to remove all agents from the model was added, and the visualisation now supports drawing the experimental discrete spaces in both matplotlib and altair. All agents which are in a space can now conveniently be accessed with .agents.

The rarely used mesa startproject cookiecutter feature was removed. We updated our best-practice guide to include how to structure a modern Mesa project, which is now very straightforward.

What's Changed

⚠️ Breaking changes

remove cookiecutter by @quaquel in mesa#2421

🧪 Experimental features

Add support for drawing discrete grids by @quaquel in mesa#2386
Altair spaces by @quaquel in mesa#2397

🎉 New features added

remove_all_agents method added to model by @quaquel in mesa#2394
Pass through model.rgn in agent analogous to model.random by @quaquel in mesa#2400
add agents property to all spaces by @quaquel in mesa#2418

🛠 Enhancements made

update_tutorial environment by @tpike3 in mesa#2411

🐛 Bugs fixed

Fix for mistaken removal of _draw_grid by @quaquel in mesa#2398
fixes weakref bug in shuffle_do by @quaquel in mesa#2399

🔍 Examples updated

refactor: Simplify Schelling code by @rht in mesa#2353
Move examples into mesa by @Corvince in mesa#2387
Explicitly test basic examples by @quaquel in mesa#2390
Make example import absolute by @quaquel in mesa#2402
Cleanup and restructure EpsteinCivilViolence and PdGrid examples by @EwoutH in mesa#2408
Reorganize advanced examples: wolf_sheep and sugarscape_g1mt by @quaquel in mesa#2410
reactivate ruff for advanced examples and include them in tests by @quaquel in mesa#2414

📜 Documentation improvements

Include examples in readthedocs (port) by @EwoutH in mesa#2392
Update into_tutorial by @tpike3 in mesa#2372
Update Schelling Readme.md by @quaquel in mesa#2406
Update Conway example by @quaquel in mesa#2403
Boltzmann readme by @quaquel in mesa#2405
Update Readme.md of Boid flockers by @quaquel in mesa#2404
add advanced examples to rtd by @quaquel in mesa#2413
Tutorial Improvements by @tpike3 in mesa#2415
space: Add note that Grids are maintenance only by @EwoutH in mesa#2420
Migration guide: Update automatic unique_id assignment examples by @EwoutH in mesa#2419
Update docstring of SimEvent by @quaquel in mesa#2417
best-practices: Update Model Layout section by @EwoutH in mesa#2424
docs: Clean-up index.md by @EwoutH in mesa#2422

🔧 Maintenance

Add empty pull_request_template.md to enable PR template chooser by @EwoutH in mesa#2409

Full Changelog: https://github.com/mesa/mesa/compare/v3.0.0b1...v3.0.0b2

3.0.0b1 (2024-10-17)

Highlights

Mesa 3.0 beta 1 is our last beta release before the Mesa 3.0 stable release. We are restructuring our examples and have move 9 core examples from mesa-examples to mesa itself (#2358). The 5 basic examples are now directly importable (#2381):

from examples.basic import BoidFlockers, BoltzmannWealthModel, ConwaysGameOfLife, Schelling, VirusOnNetwork

The 5 basic examples will always use stable Mesa features, we are also working on 4 more advanced example which can also include experimental features.

All our core examples can now be viewed in the examples folder. mesa-examples will continue to exists for user showcases. We're also working on making the examples visible in the ReadtheDocs (#2382) and on an website (mesa-examples#139). Follow all our work on the examples in this tracking issue #2364.

Furthermore, the visualizations are improved by making visualization elements scalable and more clearly labeling the plots, and the Model now has an rng argument for an SPEC 7 compliant NumPy random number generator (#2352). Following SPEC 7, you have to pass either seed or rng. Whichever one you pass will be used to seed both random.Random, and numpy.random.Generator.

What's Changed

⚠️ Breaking changes

replace model with random in AgentSet init by @quaquel in mesa#2350

🧪 Experimental features

cell space: Add convenience properties for grid width and height by @quaquel in mesa#2348
Bugfix for deepcopy / pickling discrete spaces by @quaquel in mesa#2378

🎉 New features added

Move core example models back (v2) by @EwoutH in mesa#2358
Add Model.rng for SPEC-7 compliant numpy random number generation by @quaquel in mesa#2352

🛠 Enhancements made

use GridDraggable instead of Column in SolaraViz by @wang-boyu in mesa#2344
update legend, xlabel & format of matplotlib plots by @wang-boyu in mesa#2346
init.py: Import mesa.experimental by @EwoutH in mesa#2374
Importable examples by @Corvince in mesa#2381

🐛 Bugs fixed

experimental init: Fix Solara import by making it lazy by @EwoutH in mesa#2357
fix: pass model.random to schedulers by @quaquel in mesa#2359
fix: register agent after creating unique_id and pos attributes by @wang-boyu in mesa#2368
solara: viz tutorial: fix histogram code by @Corvince in mesa#2379

🔍 Examples updated

Cleanup and restructure basic example models by @EwoutH in mesa#2365
Ruff basic examples by @EwoutH in mesa#2370

📜 Documentation improvements

Update migration_guide.md by @quaquel in mesa#2347

🔧 Maintenance

Code coverage: ignore experimental and visualization by @Corvince in mesa#2361
add codecov token, fixes #2363 by @Corvince in mesa#2366
add test_time back by @quaquel in mesa#2367
Release notes: Add example category by @EwoutH in mesa#2369

Full Changelog: https://github.com/mesa/mesa/compare/v3.0.0b0...v3.0.0b1

3.0.0b0 (2024-10-04)

Highlights

We're proud to release the first Mesa 3.0 beta! This pre-release announces that we're ready for Mesa 3.0 to be tested by all our regular users. We try to not making breaking changes anymore, but focus on resolving bugs and imperfections.

In this beta, not so much has changed as in the alphas (we're stabilizing, that's a good sign), but there are still a few notable things:

Agents now have to be initialized without their unique_id. See #2328 and the Migration guide.
PropertyLayers can now be visualized! See #2336 for details and some examples, and mesa-examples#214 as a simple example model.
We reduced the core dependencies of Mesa, so that's a lighter and simpler install. You can now use extras to install the dependencies, for example add [viz] to install all visualisation dependencies: pip install -U --pre mesa[viz]. See #2265 for details.
The Mesa Overview as fully updated for 3.0. We highly recommend reading though it!
We made some more progress on the experimental Cell Space, adding movement and integrating the PropertyLayer. Among others, Agents have nu initial movement capabilities for grids. Development continues during the betas and

We plan to release one or two more beta's in the coming weeks, and tag a release candidate and Mesa 3.0 late October. In the v3.0 milestone are the critical items on our todo-list.

You can install this pre-release as usual with:

pip install --upgrade --pre mesa

We're very curious what you think, try it out and ask any questions or share any feedback here!

What's Changed

⚠️ Breaking changes

update Agent.__init__ to remove deprecation warning by @quaquel in mesa#2328

🎉 New features added

Visualize PropertyLayers by @EwoutH in mesa#2336

🧪 Experimental features

Encapsulate cell movement in properties by @quaquel in mesa#2333
experimental: Integrate PropertyLayers into cell space by @EwoutH in mesa#2319
Generalize CellAgent by @Corvince in mesa#2292

🛠 Enhancements made

Reduce core dependencies, split in optional dependencies by @EwoutH in mesa#2265

🐛 Bugs fixed

viz: stop running and disable buttons when model.running is False by @wang-boyu in mesa#2332

📜 Documentation improvements

docs: Update overview for Mesa 3.0 by @EwoutH in mesa#2317
Readthedocs: Add version switch and update URL by @EwoutH in mesa#2324

🔧 Maintenance

tests: Resolve warnings by removing scheduler and updating arguments by @EwoutH in mesa#2329
add super call to Model and remove self.schedule by @quaquel in mesa#2334

Other changes

Deprecate initialize_data_collector by @EwoutH in mesa#2327

Full Changelog: https://github.com/mesa/mesa/compare/v3.0.0a5...v3.0.0b0

3.0.0a5 (2024-09-21)

Highlights

Mesa v3.0 alpha 5 release contains many quality of life updates, a big new feature for the DataCollector and a major deprecation.

The entire mesa.time module, including all schedulers, has been deprecated (#2306). Users are encouraged to transition to AgentSet functionality for more flexible and explicit agent activation patterns. Check the migration guide on how to upgrade.

The DataCollector now supports collecting data from specific Agent subclasses using the new agenttype_reporters parameter (#2300). This allows collecting different metrics for different agent types. For example:

self.datacollector = DataCollector(
    agenttype_reporters={
        Wolf: {"sheep_eaten": "sheep_eaten"},
        Sheep: {"wool": "wool_amount"}
    }
)

Furthermore, a new shuffle_do() method for AgentSets provides a faster way to perform shuffle().do() (#2283). The GroupBy class gained count() and agg() methods to count the number of agents in groups and aggregate variables of them (#2290).

In the experimental Cell Space, the CellCollection.select method was updated to use at_most instead of n, aligning with the AgentSet API (#2307). Additionally, the Cell class now features a dedicated neighborhood property for direct neighbors (default radius=1) and a get_neighborhood method for larger radii (#2309).

Finally, SolaraViz received updates improving its interface and performance (#2299, #2304). Cell connections in grids and networks are now public and named for more intuitive agent movements (#2296). The Model class initialization process was simplified by moving random seed and random object creation to __init__ (#1940). Documentation has been extensively updated, including enforcing Google docstrings (#2294) and reorganizing the API documentation (#2298) for better clarity and navigation.

While the Mesa 3.0 timeline is still being discussed, we're aiming at the first Mesa 3.0 beta in October followed by a stable release in November. Testing new features and sharing feedback is appreciated!

What's Changed

🎉 New features added

GroupBy: Add count and agg methods by @EwoutH in mesa#2290
datacollector: Allow collecting data from Agent (sub)classes by @EwoutH in mesa#2300
Add optimized shuffle_do() method to AgentSet by @EwoutH in mesa#2283

🛠 Enhancements made

Make cell connections public and named by @Corvince in mesa#2296
SolaraViz Updates by @Corvince in mesa#2299
Solara viz: use_task for non-threaded continuous play by @Corvince in mesa#2304

🧪 Experimental features

Update to CellCollection.select by @quaquel in mesa#2307
Have a dedicated neighborhood property and a get_neighborhood method on Cell by @quaquel in mesa#2309

📜 Documentation improvements

Enforce google docstrings by @quaquel in mesa#2294
Api docs by @quaquel in mesa#2298
update migration guide to describe solaraviz updates by @Corvince in mesa#2297
Migration Guide: Add Model initialization requirement and automatic Agent.unique_id assignment by @EwoutH in mesa#2302
Deprecate Time module and all its Schedulers by @EwoutH in mesa#2306
intro_tutorial: Don't initialize agents with an unique_id by @EwoutH in mesa#2315
Migration guide: Intro, upgrade strategy, model.agents, headers by @EwoutH in mesa#2314

🔧 Maintenance

make typing behavior of AgentSet.get explicit by @quaquel in mesa#2293
model: Move random seed and random to init by @rht in mesa#1940
Remove schedulers from benchmark models. by @quaquel in mesa#2308

Full Changelog: https://github.com/mesa/mesa/compare/v3.0.0a4...v3.0.0a5

3.0.0a4 (2024-09-09)

Highlights

Mesa 3.0.0a4 contains two major breaking changes:

The Agent's unique_id is now automatically assigned, so doesn't need to be passed to the Agent class anymore. In a subclassed custom Agent, like normally used, this now looks like this:

class Wolf(Agent):
-    def __init__(self, unique_id, model, energy=None):
+    def __init__(self, model, energy=None):
        # When initializing the super class (Agent), passing unique_id isn't needed anymore
-        super().__init__(unique_id, model)
+        super().__init__(model)

- wolf = Wolf(unique_id, model)
+ wolf = Wolf(model)

Example models were updated in mesa-examples#194, which shows more examples on how to update existing models.

Our visualisation API is being overhauled, to be more flexible and powerful. For more details, see #2278.
- An initial update to the tutorial was made in #2289 and is available here.
- An initial example model was updated in mesa-examples#195, and more examples will be updated in mesa-examples#195.
- The old SolaraViz API is still available at mesa.experimental, but might be removed in future releases.

Furthermore, the AgentSet has a new agg method to quickly get an aggregate value (for example min_energy = model.agents.agg("energy", min)) (#2266), The Model get_agents_of_type function is replaced by directly exposing the agents_by_type property (which can be accessed as a dict) (#2267, mesa-examples#190) and the AgentSet get() methods can now handle missing values by replacing it with a default value (#2279).

Finally, it fixes a bug in which the Grid's move_agent_to_one_of method with selection="closest" selected a location deterministically, instead of randomly (#2118).

What's Changed

⚠️ Breaking changes

move solara_viz back to experimental by @Corvince in mesa#2278
track unique_id automatically by @quaquel in mesa#2260

🎉 New features added

AgentSet: Add agg method by @EwoutH in mesa#2266
Implement new SolaraViz API by @Corvince in mesa#2263

🛠 Enhancements made

Model: Replace get_agents_of_type method with agents_by_type property by @EwoutH in mesa#2267
add default SolaraViz by @Corvince in mesa#2280
Simplify ModelController by @Corvince in mesa#2282
Add default values and missing value handling to agentset.get by @quaquel in mesa#2279

🐛 Bugs fixed

Fix deterministic behavior in move_agent_to_one_of with selection="closest" by @OrenBochman in mesa#2118

📜 Documentation improvements

docs: Fix Visualization Tutorial (main branch) by @EwoutH in mesa#2271
Docs: Fix broken relative links by removing .html suffix by @EwoutH in mesa#2274
Readthedocs: Don't let notebook failures pass silently by @EwoutH in mesa#2276
Update viz tutorial to the new API by @Corvince in mesa#2289

🔧 Maintenance

Resolve multiprocessing warning, state Python 3.13 support by @rht in mesa#2246

New Contributors

@OrenBochman made their first contribution in mesa#2118

Full Changelog: https://github.com/mesa/mesa/compare/v3.0.0a3...v3.0.0a4

3.0.0a3 (2024-08-30)

Highlights

Developments toward Mesa 3.0 are steaming ahead, and our fourth alpha release is packed with features and updates - only 8 days after our third.

Mesa 3.0.0a3 contains one breaking change: We now automatically increase the steps counter by one at the beginning of each Model.steps() call. That means increasing steps by hand isn't necessary anymore.

The big new features is the experimental Voronoi grid that @vitorfrois implemented in #2084. It allows creating cells in a Voronoi layout as part of the experimental cell space. An example using it to model Cholera spread can be found here.

The AgentSet got a lot of love with two brand new methods: .groupby() to split in groups (#2220) and .set() to easily assign variables to all agents in that set (#2254). The select() method is improved by allowing to select at most a fraction of the agents (#2253), and we split the do() method in do() and map() to make a distinction between the return types (#2237).

Furthermore, we improved the performance of accessing Model.agents, squashed a bug in SolaraViz, started testing on Python 3.13 and added a new benchmark model.

Our example models also got more love: We removed the RandomActivation scheduler in 14 models and removed SimultaneousActivation in 3 models (examples#183). They now use the automatic step increase and AgentSet functionality. We started testing our GIS model in CI (examples#171) and resolved a lot of bugs in them (examples#172, help appreciated!).

Finally, we have two brand new examples: An Ant Colony Optimization model using an Ant System approach to the Traveling Salesman problem, a Mesa NetworkGrid, and a custom visualisation with SolaraViz (examples#157 by @zjost). The first example using the PropertyLayer was added, a very fast implementation of Conway's Game of Life (examples#182).

To help the transition to Mesa 3.0, we started writing a migration guide. Progress is tracked in #2233, feedback and help is appreciated! Finally, we also added a new section to our contributor guide to get new contributors up to speed.

This pre-release can be installed as always with pip install --pre mesa

What's Changed

⚠️ Breaking changes

model: Automatically increase steps counter by @EwoutH in mesa#2223

🧪 Experimental features

Voronoi Tessellation based Discrete Space by @vitorfrois in mesa#2084

🎉 New features added

Add AgentSet.groupby by @quaquel in mesa#2220
AgentSet: Add set method by @EwoutH in mesa#2254

🛠 Enhancements made

Split AgentSet into map and do to separate return types by @quaquel in mesa#2237
Performance enhancements for Model.agents by @quaquel in mesa#2251
AgentSet: Allow selecting a fraction of agents in the AgentSet by @EwoutH in mesa#2253

🐛 Bugs fixed

SolaraViz: Reset components when params are changed by @rht in mesa#2240

📜 Documentation improvements

Contribution: Add "I have no idea where to start" section by @EwoutH in mesa#2258
Write initial Mesa Migration guide by @EwoutH in mesa#2257

🔧 Maintenance

CI: Add test job for Python 3.13 by @EwoutH in mesa#2173
Add pull request templates by @EwoutH in mesa#2217
benchmarks: Add BoltzmannWealth model by @EwoutH in mesa#2252
CI: Add optional dependency for examples by @EwoutH in mesa#2261

New Contributors

@vitorfrois made their first contribution in mesa#2084

Full Changelog: https://github.com/mesa/mesa/compare/v3.0.0a2...v3.0.0a3

3.0.0a2 (2024-08-21)

Highlights

In Mesa 3.0 alpha 2 (v3.0.0a2) we've done more clean-up in preparation for Mesa 3.0. We now require super().__init__() to run on initializing a Mesa model subclass, Model.agents is now fully reserved for the Model's internal AgentSet and we fixed a bug in our Solara space_drawer.

A new feature was added in #2219, which now also allows AgentSet.do() to take any callable function, instead of only a string referencing to an Agent method. The argument name was changed from method_name to method.

The new Solara visualisation now allows portraying agents in different shapes, checkout some examples in #2214.

We're also working hard on our example models. All model warnings were resolved and we've replaced a lot of schedulers with simpler and more flexible AgentSet functionality. Checkout our open issues if you want to help improve our example models further!

What's Changed

⚠️ Breaking changes

breaking: Add dependencies argument to custom space_drawer by @rht in mesa#2209
Require Mesa models to be initialized with super().__init__() by @EwoutH in mesa#2218
Allow AgentSet.do() to take Callable function by @quaquel in mesa#2219
Change warning when setting model.agents to error by @EwoutH in mesa#2225

🧪 Experimental features

devs/eventlist: Add repr method to print EventList pretty by @EwoutH in mesa#2195

🛠 Enhancements made

Visualisation: Allow specifying Agent shapes in agent_portrayal by @rmhopkins4 in mesa#2214

📜 Documentation improvements

docs/conf.py: Use modern intersphinx_mapping format by @EwoutH in mesa#2206
docs: Update Readme and tutorials to mention Mesa 3.0 pre-releases by @EwoutH in mesa#2203

🔧 Maintenance

CI: Let pytest treat warnings as errors for examples by @EwoutH in mesa#2204

New Contributors

@rmhopkins4 made their first contribution in mesa#2214

Full Changelog: https://github.com/mesa/mesa/compare/v3.0.0a1...v3.0.0a2

3.0.0a1 (2024-08-01)

Highlights

Mesa 3.0 alpha 1 (v3.0.0a1) is another step towards our next major version. This release introduces a name change from JupyterViz (jupyter_viz) to SolaraViz (solara_viz), to better represent the tech stack being used. It also includes two bugfixes also present in 2.3.2.

What's Changed

⚠️ Breaking changes

viz: Combine code for rendering in browser and Jupyter by @rht in mesa#2180

🛠 Enhancements made

Rename JupyterViz to SolaraViz by @rht in mesa#2187
refactor: Rename jupyter_viz namespace to solara_viz by @rht in mesa#2188

🐛 Bugs fixed

fix: Render agent marker radius correctly by @rht in mesa#2181
fix: Use model.schedule.steps -> mode._steps for batch_run by @rht in mesa#2183

📜 Documentation improvements

Add original conference paper link to docs by @ENUMERA8OR in mesa#2160

New Contributors

@ENUMERA8OR made their first contribution in mesa#2160

Full Changelog: https://github.com/mesa/mesa/compare/v3.0.0a0...v3.0.0a1

3.0.0a0 (2024-07-04)

Highlights

This is the first pre-release in the Mesa 3.0 series, which is still in active development. The v3.0.0a0 pre-release can help active Mesa developers help starting to test the latest features in their models.

Since it's in active development, more breaking changes may follow and it's not recommended for general usage.

There are two major breaking changes at this point:

The old visualisation is removed, in favor of the new, Solara based, Jupyter Viz. This was already available in the 2.3.x release series, but is now stabilized. Checkout out our new Visualization Tutorial. More examples and a migration guide will follow later in the Mesa 3.0 development.
The mesa.flat namespace is removed, since was not used very often.

Mesa 3.0 will require Python 3.10+.

This pre-release can be installed with pip install mesa --upgrade --pre.

What's Changed

⚠️ Breaking changes

Remove mesa.flat namespace by @rht in mesa#2091
breaking: Remove visualization_old (mesa-viz-tornado) by @rht in mesa#2133

🎉 New features added

Set JupyterViz as stable by @rht in mesa#2090

🐛 Bugs fixed

Jupyter_viz: Allow measures to be None by @EwoutH in mesa#2163
Jupyter Viz: Don't avoid interactive backend by @EwoutH in mesa#2165

📜 Documentation improvements

Fix image on landing page of docs. by @jackiekazil in mesa#2146
Replace links in docs - google group to matrix. by @jackiekazil in mesa#2148
Update visualisation docs by @EwoutH in mesa#2162

🔧 Maintenance

CI: Add weekly scheduled run to all CI workflows by @EwoutH in mesa#2130
Drop support for Python 3.9, require Python >= 3.10 by @EwoutH in mesa#2132
Add script to list unlabeled PR's since latest release by @rht in mesa#2047

New Contributors

@stephenfmann made their first contribution in mesa#2154

Full Changelog: https://github.com/mesa/mesa/compare/v2.3.1...v3.0.0a0

2.3.2 (2024-07-22)

Highlights

Mesa 2.3.2 is a small patch release which fixes two bugs, one to the batch_run function still depending on schedule.steps, and one in the agent marker visualisation.

What's Changed

🐛 Bugs fixed

fix: Render agent marker radius correctly by @rht in mesa#2181
fix: Use model.schedule.steps -> mode._steps for batch_run by @rht in mesa#2183

Full Changelog: https://github.com/mesa/mesa/compare/v2.3.1...v2.3.2

2.3.1 (2024-07-03)

Highlights

Mesa 2.3.1 is a small patch release with a datacollector bug fixed and improved documentation.

What's Changed

🐛 Bugs fixed

datacollector: store separate snapshots of model data per step by @EwoutH in mesa#2129

📜 Documentation improvements

Add experimental features to documentation as per #2122 by @stephenfmann in mesa#2154

Full Changelog: https://github.com/mesa/mesa/compare/v2.3.0...v2.3.1

2.3.0 (2024-04-23)

Highlights

Mesa 2.3.0 is a big feature release and the last feature release before 3.0.

There are two main new features:

The experimental cell-centric discrete spaces, as added in #1994. It allows having cells with not only properties but also active behaviors: the CellAgent. Its inspired by NetLogo's patches but extend and generalize this concept further.
Full support for discrete event scheduling, as added in #2066. It allows scheduling events (like Agent actions) at any time, including non-integer timesteps.

There are a lot of other features: The Jupyter visualisation now supports easier way to specify sliders, NetworkGrid.get_neighbors() supports a radius, AgentSet.get() can retrieve multiple attributes and there are now benchmarks to track Mesa performance during development.

Finally, 2.3.0 stabilizes the AgentSet (including model.agents), making it the first experimental Mesa feature that is taken out of it's experimental phase.

Install this release with:

pip install --upgrade mesa

The Mesa 2.3.x-series supports Python 3.9 to 3.12. The next major release will require Python 3.10.

What's Changed

🧪 Experimental features

Add cell-centric discrete spaces (experimental) by @Corvince in mesa#1994

🎉 New features added

Add performance benchmarking scripts by @EwoutH in mesa#1979
feat: Implement Slider class for JupyterViz by @rht in mesa#1972
Stabilize AgentSet by @EwoutH in mesa#2065
Support discrete event scheduling by @quaquel in mesa#2066

🛠 Enhancements made

JupyterViz: Automatically deduce display name from model class by @rht in mesa#1975
Add radius argument to NetworkGrid.get_neighbors() by @EwoutH in mesa#1973
Speedup of Agentset.shuffle by @quaquel in mesa#2010
feat: Let mesa runserver detect server.py as fallback by @rht in mesa#2015
JupyterViz: {Convert make_plot & prepare ColorCard} to become Solara component by @rht in mesa#2020
new feature: AgentSet.get can retrieve one or more then one attribute by @quaquel in mesa#2044
Update CODE_OF_CONDUCT.md to version 2+ of contrib covenant by @jackiekazil in mesa#2052
Improve flocking benchmark by @coderbeta1 in mesa#2054
Remove JupyterViz Altair marker overlap for huge grid size by @rht in mesa#2062
Add tooltip option to Altair chart by @FoFFolo in mesa#2082
feat: Display model seed & allow user to specify it in JupyterViz by @rht in mesa#2069
warn if placing already placed agent by @puer-robustus in mesa#2083

🐛 Bugs fixed

fix: Apply default value to slider by @rht in mesa#2016
fix: Initialize model _steps and _time during new by @rht in mesa#2026
fix: Use model.schedule only when it is not None by @rht in mesa#2050
fix: Remove JupyterViz grid marker overlap for huge grid size by @rht in mesa#2049

📜 Documentation improvements

Improve readability of badges by @rht in mesa#2009
More pythonic implementation of wolf sheep by @quaquel in mesa#2011
Adding super().init() to MoneyModel tutorial by @sw23 in mesa#2025
docs: Convert howto.rst -> howto.md via rst2myst by @rht in mesa#2033
docs: Convert best-practices,overview,packages,mesa,index to .md via rst2myst by @rht in mesa#2034
docs: Convert api/.rst -> api/.md via rst2myst by @rht in mesa#2035
docs: Rewrite howto.md using ChatGPT for clarity and conciseness by @rht in mesa#2037
docs: Corrected Contributing Guide Link to Ensure Accessibility by @sahusiddharth in mesa#2057
Rename links to internal .rst files to .md by @rht in mesa#2058
docs: improve introductory tutorial by @puer-robustus in mesa#2087

🔧 Maintenance

Quality of Life: Make codecov less meticulous by @Corvince in mesa#1966
Add CI workflow for performance benchmarks by @EwoutH in mesa#1983
tests: Resolve warnings by defining PropertyLayer dtypes by @EwoutH in mesa#1987
benchmarks.yml: Fix PR branch checkout when triggered by comment by @EwoutH in mesa#1998
Quality of life: automatically fix ruff errors by @Corvince in mesa#2004
benchmarks.yml: Run on addition of label instead of comment by @EwoutH in mesa#2002
ci: Move codespell to pre-commit by @rht in mesa#2040
Schelling by @coderbeta1 in mesa#2053
Move ruff lint settings into dedicated section by @Corvince in mesa#2073
ci: Use uv pip for faster build by @rht in mesa#2038
test: Remove place_agent duplicate warnings by @rht in mesa#2086

Other changes

Minor edits to benchmarking code by @quaquel in mesa#1985
build(deps): bump codecov/codecov-action from 3 to 4 by @dependabot in mesa#2030
[pre-commit.ci] pre-commit autoupdate by @pre-commit-ci in mesa#2029
tests: Speed up test_batch_run by @rht in mesa#2039
Update benchmarks.yml by @Corvince in mesa#2043
docs: Convert visualization .rst -> .md via rst2myst by @rht in mesa#2036
docs: Convert CONTRIBUTING .rst -> .md via rst2myst by @rht in mesa#2041
Correct wolf energy gained from eating sheep by @JackAtOmenApps in mesa#2048
feat: Implement Altair version of grid visualization by @rht in mesa#1991

New Contributors

@sw23 made their first contribution in mesa#2025
@JackAtOmenApps made their first contribution in mesa#2048
@coderbeta1 made their first contribution in mesa#2054
@sahusiddharth made their first contribution in mesa#2057
@FoFFolo made their first contribution in mesa#2082
@puer-robustus made their first contribution in mesa#2083

Full Changelog: https://github.com/mesa/mesa/compare/v2.2.4...2.3.0

2.3.0-rc1 (2024-04-18)

Mesa 2.3.0-rc1 is pre-release in preparation for 2.3.0 stable. It had the same release notes as 2.3.0.

2.2.4 (2024-01-26)

Highlights

Mesa v2.2.4 is a small but important bugfix release for the 2.2 release series. It fixes an essential bug in where agents weren't shuffled in the BaseScheduler, affecting mainly the RandomActivation scheduler (effectively making it sequential activation)(#2007). It also fixes a small behaviour change in RandomActivationByType.agents_by_type() (#1996). Furthermore, this release adds an internal clock to the Model, which allows to use a Mesa model without a scheduler (using the AgentSet API)(#1942).

Updating from previous 2.2 releases is highly recommended, especially when using the RandomActivation scheduler.

What's Changed

🛠 Enhancements made

refactor: Remove dependence on model.schedule, add clock to Model by @rht in mesa#1942

🐛 Bugs fixed

Fix AgentSet inplace shuffle (and thus RandomActivation), add tests by @EwoutH and @quaquel in mesa#2007
fix: Reverse dict key and value for agents_by_type by @rht in mesa#1996

Full Changelog: https://github.com/mesa/mesa/compare/v2.2.3...v2.2.4

2.2.3 (2024-01-22)

Highlights

Mesa 2.2.3 is a small release with two improvements to the experimental Solara visualisation, on request of one of our contributors. No stable features have changed.

What's Changed

🧪 Experimental features

solara_viz: Add borders around ContinuousSpace by @EwoutH in mesa#1988

🐛 Bugs fixed

fix: Explicitly specify JupyterViz space view limits by @rht in mesa#1984

Full Changelog: https://github.com/mesa/mesa/compare/v2.2.2...v2.2.3

2.2.2 (2024-01-22)

Highlights

Mesa 2.2.2 is a small bugfix release, for models in which users had defined Model.agents (self.agents in a Model (sub)class). This is deprecated, but for now allowed. See #1919 (comment).

What's Changed

🐛 Bugs fixed

Allow user models to assign Model.agents for now, but add warning by @quaquel in #1976

Full Changelog: https://github.com/mesa/mesa/compare/v2.2.1...v2.2.2

2.2.1 (2024-01-16)

Highlights

After the huge 2.2.0 release we are releasing 2.2.1 which addresses a few bugs, unintended behaviors and a performance regression. #1960 makes sure agent addition and removal is handled correct, #1965 fixed an unintended behavior change in RandomActivationByType.agents_by_type and #1964 makes sure we're at least as fast as before 2.2.0, if not faster. The introduction tutorial is also extended with #1955.

We highly recommend updating to 2.2.1 if you're using 2.2.0.

What's Changed

🧪 Experimental features

jupyter_viz: Implement multiline plot by @rht in mesa#1941

🛠 Enhancements made

make mesa runnable without some dependencies by @Corvince in mesa#1950
Improve performance of AgentSet and iter_cell_list_contents by @Corvince in mesa#1964

🐛 Bugs fixed

Bugfix in agentset to handle addition and removal correctly by @quaquel in mesa#1960
Make RandomActivationByType.agents_by_type backward compatible by @quaquel in mesa#1965

📜 Documentation improvements

Refer to just Python instead of Python 3 by @rht in mesa#1957
intro tutorial: Analysing model reporters by @EwoutH in mesa#1955

🔧 Maintenance

Migrate from setuptools to hatch by @rht in mesa#1882
ci: Add tests for mesa-examples by @rht in mesa#1956
refactor: Move Matplotlib-specific Solara components to separate file by @rht in mesa#1943

Full Changelog: https://github.com/mesa/mesa/compare/v2.2.0...v2.2.1

2.2.0 (2024-01-09)

Highlights

The 2.2.0 release of the Mesa library introduces several updates and new features for managing and scheduling agents and modelling the environment, along with an experimental release policy aimed at enhancing development speed and community feedback. Below are key highlights of the new (experimental) features in this release. Mesa 2.2.0 supports Python 3.9+.

Despite the minor version number, this is one of our biggest releases yet.

Experimental feature policy (discussion #1909)

This release introduces an experimental feature policy aimed at accelerating development and gathering community feedback. Features like #1890, #1898, and #1916 are marked as experimental under this policy.

Policy overview:

Experimental features can be added or changed in any release, even patch releases.
They don’t need a diligent review for every change, allowing for quicker development cycles.
Community feedback is encouraged through discussion threads.

Native support for multiple Agent types (PR #1894)

This update introduces a agents variable to the Mesa Model class, offering a first step in supporting multiple agent types as first class citizens. Each Model is now initialized with an self.agents variable (an AgentSet) in which all the agents are tracked. You can now always ask which agents are in the model with model.agents. It's the foundation which will allow us to solve problems with scheduling, data collection and visualisation of multiple agent types in the future.

🧪 AgentSet class (PR #1916)

The new AgentSet class encapsulates and manages collections of agents, streamlining the process of selecting, sorting, and applying actions to groups of agents.

Key features:

Flexible and efficient agent management and manipulation.
Methods like select, shuffle, sort, and do for intuitive operations.

Example:

# Applying a method to each agent
model.agents.do('step')

# Filtering and shuffling agents
shuffled_agents = model.agents.select(lambda agent: agent.attribute > threshold).shuffle()

The AgentSet is an experimental feature. We would love feedback on it in #1919.

🧪 PropertyLayer and _PropertyGrid (PR #1898)

The introduction of PropertyLayer and the extension of SingleGrid and MultiGrid classes to support cell properties mark a significant enhancement in Mesa's environmental modeling capabilities. It allows to add different layers of variables to grids, that can be used to represent spatial environmental properties, such as elevation, pollution, flood levels or foliage.

Key features:

Efficient management of environmental properties like terrain types and resources.
Dynamic interaction between agents and their environment.
Fast modification and selection of cells based on one or multiple properties

Example:

from mesa.space import SingleGrid, PropertyLayer

grid = SingleGrid(10, 10, False)
property_layer = PropertyLayer("elevation", 10, 10, default_value=0)
grid.add_property_layer(property_layer)

# Modify multiple cells values
grid.properties["elevation"].modify_cells(np.multiply, 2)

# Select cells that have an elevation of at least 50
high_elevation_cells = grid.properties["elevation"].select_cells(condition=lambda x: x > 50)

The PropertyLayer is an experimental feature. We would love feedback on it in #1932.

🧪 DiscreteEventScheduler (PR #1890)

The DiscreteEventScheduler is an innovative addition to the Mesa time module, tailored for discrete event simulations. This scheduler advances simulations based on specific event timings rather than regular intervals, providing more flexibility in modeling complex systems.

Key Features:

Efficient handling of events scheduled for specific simulation times.
Randomized execution order for events scheduled at the same time.

The DiscreteEventScheduler is an experimental feature. We would love feedback on it in #1923.

What's Changed

🧪 Experimental features

Native support for multiple agent types by @EwoutH in mesa#1894
space: Implement PropertyLayer and _PropertyGrid by @EwoutH in mesa#1898
Add DiscreteEventScheduler by @EwoutH in mesa#1890

🎉 New features added

Introduce AgentSet class by @EwoutH in mesa#1916

🛠 Enhancements made

Reimplement schedulers to use AgentSet by @quaquel in mesa#1926
space: Let move_agent choose from multiple positions by @EwoutH in mesa#1920

🐛 Bugs fixed

Work around for initializing model._agent by @quaquel in mesa#1928
Honor disabled space drawer option when rendering in the browser by @rlskoeser in mesa#1907

📜 Documentation improvements

Document empties property by @EwoutH in mesa#1888
docs: Fix README.md inline code formatting by @rht in mesa#1887

🔧 Maintenance

ci: Speed up pip install by caching deps install output by @rht in mesa#1885
Create release.yml file for automatic release notes generation by @EwoutH in mesa#1925
Drop support for Python 3.8 by @rht in mesa#1756

New Contributors

@quaquel made their first contribution in mesa#1928

Full Changelog: https://github.com/mesa/mesa/compare/v2.1.5...v2.2.0

2.1.5 (2023-11-26)

This release has some critical fixes to JupyterViz/Solara frontend to prevent flickering and improve the display of the jupyter plots. It also has improvements to datacollection and the documentation.

Improvements

datacollection: check if model reporters is a partial function (#1872)

Docs and Tutorial

docs: convert README from .rst to .md (#1881)
docs: convert HISTORY from .rst to .md (#1873)
docs: enhance docstrings for scheduler classes in mesa.time (#1866)

CI and WorkFlows

ci: Remove redundant Ruff workflow from GitHub Actions (#1880)
Replace Black with ruff format (#1880)
Migrate setup from setup.py to pyproject.toml (#1870)

Solara/JupyterViz

fix: Do render_in_jupyter on Colab env (#1884)
Convert make_space into Solara component (#1877)
remove controls for dragging and resizing (#1878)
Improve ColorCard layout (#1876)
refactor: Define current_step as reactive (#1875)
fix: optimize controller and plots to fill screen in jupyter (#1868)
fix: ensure space and plot subcomponent are not rendered on step (#1867)

2.1.4 (2023-11-7)

This release updates mesa-viz-tornado dependency v0.1.3. This removes the external JavaScript templates and prevents 404 errors

bugfix: ensure mesa_viz_tornado>=0.1.3 #1862

2.1.3 (2023-11-5)

This release contains several improvements, fixes, and new features to the JupyterViz/Solara frontend. It's a patch release instead of a minor release because the JupyterViz frontend is still considered experimental.

Improvements

model: ensure model is initialized with random seed based #1814
space: check if position values are tuples #1831
datacollection: add agent collection by type, documentation, and tests #1838

Docs and Tutorial

tutorial: explain how to set up reporter for multiple agents #1717
docs: rename useful snippets to how to guide #1839

CI and WorkFlows

Release CI: update to run workflows on releases #1479
CI: Update GHA workflows with Python 3.12 #1840
update ruff version #1824, #1841
Ensure mesa_viz_tornado>=0.1.2 #1860

Solara/JupyterViz

perf: increase speed of Solara render #1819
implement drawer for continuous space and refactor code #1830
fix: configure change handler for checkbox input #1844
fix: ensure playing starts after model param change #1851

2.1.2 (2023-09-23)

This release contains fixes, and several improvements and new features to the JupyterViz/Solara frontend. It's a patch release instead of a minor release because the JupyterViz frontend is still considered experimental.

Improvements

perf: Access grid only once #1751
docs: compile notebooks at build time #1753
docs: Remove nbsphinx and explicit .ipynb suffix #1754
rtd: Use gruvbox-dark as style #1719
build(deps): bump actions/checkout from 3 to 4 #1790

Solara/JupyterViz

solara: Implement visualization for network grid #1767
Add support for select input type #1779
Add step count display to JupyterViz #1775
Simplify solara code #1786
Add docstring for jupyterviz make_user_input that documents supported inputs #1784
Revise, test, & document JupyterViz options for drawing agent space #1783
Add UserInputs component #1788
Fix: Remove dict merge operator, python 3.8 compat #1793
feat: Add reset button to JupyterViz #1795
Add support for solara.Checkbox user input #1798
viz tutorial: Update custom plot to reflect new code #1799
fix: Don't continue playing when a model is reset #1796
Docker: Update to use Solara viz #1757

Refactors

Move viz stuff to mesa-viz-tornado Git repo #1746
simplify get neighborhood #1760
remove attrgetter performance optimization #1809

Fixes

fix: Add Matplotlib as dependency #1747
fix install for visualization tutorial in colab #1752
fix: Allow multiple connections in Solara #1759
Revert "Ensure sphinx>=7" #1762
fix README pic to remove line on left side #1763
space: Ensure get_neighborhood output & cache are immutable #1780
fix: Use .pytemplate for name for cookiecutter #1785
HISTORY.rst: Correct neighbor_iter() replacement in 2.0.0 #1807
docs: Always link to stable version #1810
Remove exclude_none_values #1813

2.1.1 (2023-08-02)

This release improves the introductory and visualization tutorial. Ensures both are Google Colab compatible with working badges.

Changes:

: - Update intro_tutorial to warn users to ensure up to date version, and make colab compatible #1739, #1744 - Improve new/experimental Solara based visualization to ensure pause button works #1745 - Fix bug in space.py -> get_heading() #1739

2.1.0 (2023-07-22) Youngtown

This release creates mesa.experimental namespace, this solves the issue that PyPI release will not allow git-based install.

Users should read the Mesa 2.0.0 release note (directly below this), as this contains the details about the breaking changes and other major changes that were part of Mesa 2.0 release.

Changes:

: - Creates mesa.experimental namespace #1736 - Fix Ruff lint error #1737 - Update permissions for PyPI #1732

2.0.0 (2023-07-15) Wellton

Special notes

Mesa 2.0 includes:

: - an experimental pure python user interface/ visualization that is also jupyter compatible please see the visualization tutorial_ - an improved datacollector that allows collection by agent type - several breaking changes that provide significant improvements to Mesa.

Breaking Changes:

space: change coord_iter to return (content,(x,y)) instead of (content, x,y); this reduces known errors of scheduler to grid mismatch #1566, #1723
space: change NetworkGrid get_neighbors to get_neighborhood; improves performance #1542
space: raise exception when pos is out of bounds in Grid.get_neighborhood #1524

space: remove deprecations (#1520, #1687, #1688):

:   -   `find_empty()`: convert this to `move_to_empty()`
    -   `num_agents`: removed parameter from `move_to_empty()`
    -   `position_agent()`: convert this to `place_agent`
    -   `neighbor_iter()`: convert this to `iter_neighbors()`

batchrunner: remove deprecations #1627

:   -   `class BatchRunner` and `class BatchRunnerMP`: convert these
        to `batch_run()`
    -   Please see this `batch_run() example`\_ if you would like to
        see an an implementation.

visualization: easier visualization creation #1693

:   -   `UserSettableParameter(['number', 'slider','checkbox', 'choice', 'StaticText'])`:
        convert to `NumberInput` , `Slider`, `CheckBox`, `Choice`,
        `StaticText`
    -   Please see this `visualization example`\_ if you would like
        to see an implementation.

New Features:

datacollector: can now handle data collection by agent type #1419, #1702
time: allows for model level StageActivation #1709
visualization: ChartModule can have dynamically named properties #1685
visualization: improved stop server to end visualizations #1646
experimental python front end option: integrated the initial prototype of the pure python front end option #1698, #1726

Improvements

update HexGrid and create HexSingleGrid and HexMultiGrid #1581
correct get_heading for toroidal space #1686
update slider to start at 1FPS #1674
update links to examples repo due to creation of mesa_examples #1636, #1637

** CI Improvements**

:   -   update Ruff #1724
    -   remove Pipfile and Pipfile.lock #1692
    -   enable Codespell in Jupyter #1695
    -   improve regex for better build #1669, #1671
    -   exclude notebooks form linter #1670
    -   updated pip for zsh #1644
    -   CLI quality of life improvements #1640

**Docs Improvements**

:   -   update to PyData theme #1699
    -   remove .rst to create simpler build #1363, #1624
    -   use seaborn in tutorials #1718
    -   fix types and errors in docs #1624, #1705, #1706, #1720
    -   improve tutorials #1636, #1637, #1639, #1641, #1647, #1648,
        #1650, #1656, #1658, #1659, #1695, #1697,
    -   add nbsphinx to adv_tutorial #1694
    -   replace `const chart` for `var chart` in advanced tutorial
        #1679

update LICENSE to 2023 #1683

1.2.1 (2023-03-18)

This release fixes mesa#1606, where mesa startproject doesn't work.

Changes:

fix: Include cookiecutter folders in install content #1611
Fix Ruff errors and pin Ruff version #1609
datacollector: Add warning when returning empty dataframe with no reporters defined #1614

1.2.0 (2023-03-09) Taylor

Special notes

New features:

Implement radius for NetworkGrid.get_neighbors #1564

Some highlights for the perf improvements:

Use getattr for attribute strings in model data collection #1590 this is a 2x speedup over the relevant line
Faster is_integer function for common cases #1597 is for 1.3x speedup for grid access (grid[x, y])
Refactor iter/get_cell_list_contents methods #1570 at least 1.3x speedup for iter/get_cell_list_contents
Evaluate empties set more lazily #1546 (comment) ~1.3x speedup for place_agent, remove_agent, and move_agent

Improvements

ci: Add testing on Python 3.11 #1519
Remove auto-update GH Actions for Pipfile.lock #1558

ruff

:   -   ruff: Add isort #1594
    -   ci: Replace flake8 with Ruff #1587
    -   ruff: Add more rules based on Zulip\'s config #1596

perf: faster is_integer function for common cases #1597
Remove _reporter_decorator #1591
Change index at DataFrame creation in get_agent_vars_dataframe #1586
Make Grid class private #1575
Make the internal grid and empties_built in Grid class private #1568
Simplify code in ContinuousSpace #1536
Improve docstrings of ContinuousSpace #1535
Simplify accept_tuple_argument decorator in space.py #1531
Enhance schedulers to support intra-step removal of agents #1523
perf: Refactor iter_cell_list_contents Performance #1527
Replace two loops with dictionary comprehension, list- with generator comprehension #1458
Make MultiGrid.place_agent faster #1508
Update space module-level docstring summary #1518
Update NetworkGrid.__init__ docstring #1514
Deprecate SingleGrid.position_agent #1512
Make swap_pos part of Grid instead of SingleGrid #1507
Refactor NetworkGrid docstrings and iter/get_cell_list_contents #1498
Hexgrid: use get_neighborhood in iter_neighbors #1504
Auto update year for copyright in docs #1503
Refactor Grid.move_to_empty #1482
Put "Mesa" instead of "it" in README #1490
Batchrunner: Remove unnecessary dict transformation, .keys() in len() #1460
Add Dependabot configuration for GitHub Actions update check #1480
Use list transformation only when shuffled is True #1478
Implement swap_pos #1474
Clean up DataCollector #1475

Fixes

Update resources in README #1605
Fix accident from mesa#1488 #1489
pre-commit autoupdate #1598, #1576, #1548, #1494
Fix docstring of DataCollector #1592
Update Pipfile.lock (dependencies) #1495 #1487

build(deps):

:   -   build(deps): bump codecov/codecov-action from 2 to 3
        dependencies Pull requests that update a dependency file
        #1486
    -   build(deps): bump actions/upload-artifact from 2 to 3
        dependencies Pull requests that update a dependency file
        #1485
    -   build(deps): bump peter-evans/create-pull-request from 3 to
        4 dependencies Pull requests that update a dependency file
        #1484
    -   build(deps): bump actions/setup-python from 3 to 4
        dependencies Pull requests that update a dependency file
        #1483

Establish reproducibility for NetworkGrid.get_neighbors when radius > 1 #1569
Format js code #1554
Add some missing const declarations #1549
fix tutorial url in examples #1538
Update cookiecutter to flat import style. #1525
Fix bug in Grid.get_neighborhood #1517
Revert changes of #1478 and #1456 #1516
Fix return types of some NetworkGrid methods #1505
Update year for copyright #1501
Add default_value function to NetworkGrid #1497
Remove extraneous spaces from docstrings in modules 2 #1496
Remove extraneous spaces from docstrings in modules #1493
SingleGrid: Remove extraneous attribute declaration (empties) #1491

1.1.1 (2022-10-21)

This release fixes mesa#1461 where custom user-specified portrayal images don't load in the visualization server.

1.1.0 (2022-10-10) Safford

Special notes

Perf: ContinuousSpace: speed-up add/remove agents #1376. This is a ~6x performance improvement for add/remove.
fix: time: Recompute agent_keys between stages #1391. This is a correctness fix for SimultaneousActivation and StagedActivation when agents are being removed during simulation.
ModularServer: Always set model.running = True on reset #1399. With this change, specifying self.running = True in your model __init__ is now optional. Mesa's visualization server will automatically sets it to True in the beginning of a simulation.
feat: Allow user-specified local dir to be served by Tornado #1435. This simplifies the usage of ModularServer in Mesa-Geo.
Allow batch_run to take arbitrary parameters #1413. With this change, you can finally use any arbitrary Python objects as batch_run parameters, where previously they are restricted to hashable objects only.
Prevent seed and random from being shared between instances #1439. With this fix, a model instance has their own isolated RNG.

Improvements

CI Updates

:   -   ci: Cancel previous obsolete runs #1378
    -   ci: update black to prevent click error #1382
    -   Add \"falsy\" to .codespellignore #1412
    -   Upgrade pre-commit CI (with pyupgrade and syntax checks)
        #1422

Tests

:   -   test: RandomActivationByType: Test adding agents with
        duplicate ID #1392

Dependency updates

:   -   Update Pipfile.lock (dependencies) #1398
    -   Update Pipfile.lock (dependencies) #1408
    -   Update Pipfile.lock (dependencies) #1434

Docs

:   -   docs: Add Tim Pope\'s guideline for proper Git commit msg
        #1379
    -   readme: Improve the pip install for Git repo instruction
        #1416
    -   Docs: Remove trailing whitespaces #1421
    -   Fixes #1423 - fixes build badge in docs #1424

Refactors

:   -   refactor: Apply pyupgrade \--py37-plus #1429
    -   refactor ModularServer (moving code into \_\_init\_\_) #1403

Perf: ContinuousSpace: speed-up add/remove agents #1376
Remove monospace formatting for hyperlinks #1388
ModularServer: Always set model.running = True on reset #1399
Allow batch_run to take arbitrary parameters #1413
ModularServer: Put new optional arg port last #1432
feat: Allow user-specified local dir to be served by Tornado #1435
Improve and measure speed of clamp function #1440

Fixes

Fix stray " in modular_template.html #1380
Fix zoom on network visualisation #1381
Fix broken monospace links #1387
fix: Ensure agent id is unique in RandomActivationByType.add #1386
fix: time: Recompute agent_keys between stages #1391
Fix batchrunner progress bar #1395
Fix stray " in visualisation dropdown labels #1409
space: Fix type error for Python < 3.9 #1430
Prevent seed and random from being shared between instances #1439

1.0.0 (2022-07-06) Quartzsite

Special notes

BREAKING: Rename mesa.visualizations.TextVisualization.TextElement to ASCIIElement
POTENTIALLY BREAKING: Default batch_run to 1 CPU #1300
Simplified namespace implements - see Improvements section.

Improvements

Implement simplified namespace

:   -   docs: simplified namespace tutorial update #1361
    -   examples: Convert shape_example, sugarscape_cg,
        virus_on_network, wolf_sheep to simple namespace #1339
    -   Convert hex_snowflake, pd_grid, schelling to simple
        namespace; \[BREAKING\] Remove class name collision #1333
    -   examples: Convert color_patches, conways_game_of_life,
        epstein_civil_violence, forest_fire to simple namespace
        #1331
    -   Examples: Convert boltzmann_wealth_model_network and chart
        to simple namespace #1322
    -   examples: Convert boid_flockers, boltzmann_wealth_model to
        simple namespace #1321
    -   examples: Convert bank_reserves to simple namespace #1317
    -   add batch_run to simple namespace #1316
    -   Implement simpler Mesa namespace #1294

mypy

:   -   mypy: Use \"\|\" operator instead of Union/Optional #1345
    -   mypy: Improve space.py annotation, part 2 #1219
    -   mypy: Improve annotations #1212

Userparam class updates

:   -   feat: Implement NumberInput UserParam class #1343

    -   feat: Implement StaticText UserParam #1342

    -   feat: Implement Choice UserParam class #1338

    -   feat: Implement Checkbox UserParam class #1332

    -

        feat: Implement Slider UserParam class #1272

        :   -   examples: Convert to using Slider UserParam class
                #1340

Front-end updates

:   -   frontend: Add alignment options to agent portrayals in
        CanvasGridVisualization #1349

    -   frontend: Update Bootstrap 4.6.1 -\> 5.1.3 #1325

    -   ChartModule.js: Use more semantic HTML element creation
        method #1319

    -   Issue #1232; Replaced usage of var to const/let in some
        files #1248

    -   \[Issue 1232\] Refactor NetworkModuleSigma PieChartModule
        TextModule JS #1246

    -   js: Update D3 from 4.13.0 to 7.4.3 #1270

    -   support package and local css includes #1283

    -   Upgrade to Bootstrap 4! #1282

    -   refactor: update var to const/let in InteractionHandler.js
        #1273

    -   Change remaining vendored JS dependencies to be downloaded
        during install #1268

    -   Download jQuery and D3 during install #1260

    -   CSS support for custom visualization element #1267

    -   style: prettify js files #1266

    -   refactor: Change var to const/let for remaining js files
        #1265

    -   Remove NetworkModule_sigma and its dependencies #1262

    -   js: Download bootstrap-slider during install #1257

    -   js deps: Move Bootstrap to be inside external folder #1236

    -   Apply prettier to NetworkModule_d3.js #1225

    -   js: Download Bootstrap on-the-fly during install instead
        #1220

    -   Install JS dependencies using Fanstatic #1195

    -

        JQuery updates

        :   -   examples: Remove all usage of jQuery #1356
            -   Remove jQuery dependency completely #1355
            -   refactor: frontend: Remove remaining usage of jQuery
                #1351
            -   refactor: frontend: Remove usage of jQuery for most
                of the JS code #1348
            -   refactor: frontend: Remove jQuery usage in
                CanvasHexModule.js & CanvasModule.js #1347
            -   refactor: frontend: Remove jQuery usage in
                BarChartModule.js #1326
            -   visualization: Specify tooltip without jQuery #1308

CI Updates

:   -   ci: Ensure wheel is install before pip install step #1312
    -   Fix contributing (increasing black version) #1303
    -   ci: Disable PyPy for now #1254
    -   CI: Update checkout, setup-python and cache actions to v3
        #1217
    -   CI: Split off codespell job, don\'t run build on doc changes
        #1170
    -   ci: Add 6 min timeout for the test jobs #1194
    -   CI: test flake: batch runner sometimes takes 6 hours then
        gets killed by GitHub Actions #1166
    -   ci: Enable cache for all Python versions 🇺🇦 #1177
    -   CI: Create Action to publish to PyPI on release #1169
    -   CI: Python 3.6 should be removed because it has reached EOL
        #1165
    -   Update Black formatting (no spaces for power operator) #1160
    -   Improve code quality with static analysis #1328
    -   CI test: Increase timeout to 10 minutes #1250

Dependency updates

:   -   build(deps): bump cookiecutter from 2.1.0 to 2.1.1
        dependencies #1360
    -   Update Pipfile.lock (dependencies) #1374, #1350, #1301,
        #1224, #1203, #1135 by github-actions bot
    -   Migrate D3 from v4 to v7 #1088

Other Improvements

:   -   feat: Implement auto-conversion of function to TextElement
        #1346
    -   Readme: Add Matrix badge and description #1164
    -   examples: Convert nodes to list when drawing random
        sample#1330
    -   examples: Use nicer color for bank_reserves #1324
    -   examples: Use nicer color for chart #1323
    -   model: Implement initialize_data_collector #1287
    -   CONTRIBUTING: Add instruction to enable git pull autorebase
        #1298
    -   Improve MANIFEST.in #1281
    -   refactor: Merge \_remove_agent into remove_agent #1245
    -   examples: Remove usage of internal method \_remove_agent
        #1241
    -   refactor: Make \_place_agent args consistent with
        place_agent #1240
    -   Redirect user to GH discussions for seeking help #1237
    -   setup.py: Update setup classifiers and add python_requires
        for Python\>=3.7 #1215
    -   The tutorial.rst doesn\'t mention that the Pandas DataFrame
        output can be in CSV #1148
    -   Deprecate neighbor_iter in favor of iter_neighbors #1184
    -   Add snippet about using numpy\'s random #1204
    -   docs: make windows multiprocessing code appear #1201
    -   Capitalize CSV whenever applicable #1200
    -   update intro tutorial for pandas and CSV and batch_run and
        windows #1196
    -   docker-compose.yml: Make it consistent with Dockerfile #1197
    -   Improve Dockerfile #1193
    -   update to include Matrix and GitHub discussion links #1179
    -   Update docs to remove old discussion forums #1171
    -   Add \"Grass\" curve to wolf_sheep example chart #1178
    -   feat: Implement random activation by type #1162

Fixes

Git tags out of sync with conda and PyPi (0.8.8 and 0.8.9 missing on git) #1076
fix: Remove mesa.visualization.Number #1352
CI: the "install dependencies" step is slow #1163

Readme related

:   -   readme: Clarify/Update Docker instruction #1222, #1214
    -   Readme: Fix links to docs #1205

Add mesa/visualization/templates/js/external to gitignore #1320
fix: sugarscape_cg: Use better way to check if a cell is occupied by SsAgent #1313
fix double multiply of iterations in singleprocess #1310
pre-commit: fix required python version, correct example commit message... #1302
fix: Make bank_reserves batch_run example work #1293
Fixes #498. Replaces canvas_width with grid_rows to fill out color patches 3 - Accept easy task!!! #989
update pre-commit to include jupyter; fix warning #1190
fix: Grid.__getitem__: Handle Numpy integers #1181
fix: Make argument order in example models consistent #1176
issue template: Linkify discussions url #1239
batch_run: Do not iterate values when it is a single string #1289
examples: Clarify install instruction in wolf_sheep #1275
test: Disable batchrunnerMP (CI: test flake: batch runner sometimes takes 6 hours then gets killed by GitHub Actions #1166) #1256
examples: correcting comment in examples/pd_grid/pd_grid/agent.py #1247
space: Clarify the return object of get_cell_list_contents #1242
width and height were changed up #1149
fix typo in best-practices.rst #1368
fix: examples: Make space x, y order consistent #1366

0.9.0 (2022-01-31) Page

Improvements

Update number_processes and associated docs #1141
[PERF] Improve move_to_empty performance #1116
Adding logic to check whether there is agent data #1115
Convert all text strings to f-strings #1099
Format Python and Jupyter Notebook files with Black #1078
README: Add info on how to cite Mesa #1046
Re-Implementation of BatchRunner #924

CI Related

:   -   CI: Add workflow to update Pipfile.lock every month #1018
    -   CI: Lint typos with Codespell #1098
    -   CI: Only run Codecov on Ubuntu jobs and update to v2 #1083
    -   CI: Maintenance: Update to Python 3.10, split of lint jobs
        #1074

Dependency updates

:   -   Updates to Pipfile.lock (dependencies) #1114, #1086, #1080
    -   Update Pipfile to use Python 3.9 #1075
    -   Update Chart.js to 3.6.1 (v3) #1087
    -   Update Chart.js to version 2.9.4 #1084
    -   Pyupgrade 3.6: Update syntax with Python 3.6+ features #1105
    -   Bump urllib3 from 1.26.2 to 1.26.5 #1043
    -   Update packages.rst #1068

Docs

:   -   Update docs/README.md #1118
    -   Update number_processes and associated docs #1141
    -   Update section \'Batch Run\' of introductory tutorial #1119
    -   Readme: Add command to install specific branch #1111
    -   Docs: Add back some comments in space.py #1091
    -   Docs: Remove trailing white spaces #1106
    -   Update intro_tutorial.rst #1097, #1095
    -   Tweaking and improving the documentation #1072

Fixes

Rename i_steps -> data_collection_period and add docstring #1120
bank_reserves: Say that the commented out legacy code is for comparison #1110
Fix broken image on PyPI #1071

Docs

:   -   Fix numbering typos in docs/README.md #1117
    -   Readme: Fix command for installing custom branch on fork
        #1144
    -   Docs: space.py: Fix single case of neighbor spelled as
        neighbour #1090

0.8.9 (2020-05-24) Oro Valley

Note: Master branch was renamed to Main on 03/13/2021

Improvements

Master to Main change:

:   -   Docs/examples: Update links to use main instead of master as
        branch #1012
    -   CI: Run on pushed to main and release branches #1011

Github Actions

:   -   GitHub Actions: run black only on ubuntu 3.8 #996
    -   GA: Only run CI when pushed to master #974
    -   GA: Add pypy3 #972
    -   rename github action to \"build\", remove redundant flake8
        check #971
    -   GA: Run on Windows and macOS #970
    -   Add GitHub Action for continuous integration testing #966

[PERF] Add neighborhood cache to grids and improve iter_cell_list_contents #823
forest_fire: Remove unnecessary code #981
Migrate away from type comments #984
Update License #985
Public remove_agent function for NetworkGrid #1001
Date update to release #962
Advanced indexing of grid #820

Fixes

Correct spelling #999
Update Pipfile.lock #983
Fix order of variable_params in model and agent vars data frames #979
Fix asyncio on windows with python 3.6 #973

0.8.8 (2020-11-27) Nogales

Note: This is the last version to support Python 3.5.

Improvements

Added pre-commit to automatically maintain a standard formatting with black #732

Fixes

MultiGrid: Set to using list for cell content #783

Docs

:   -   Fixed broken link to templates list in advanced tutorial.
        #833
    -   Fixed image links in rst #838
    -   Cleaned html to attempt correct build #839
    -   Fixed links on Boltzmann model #843
    -   Documentation update - batchrunner & data collector #870
    -   Deleted readthedocs.yml #946
    -   Doc builds #837, #840, #844, #941, #942

Fixed bulleted list in contribution read me #836
Updated test_examples.py, changed unused generator expression to actually run the models. #829
Fixed #827 issue (example Epstein Civil Violence Jupyter Notebook typos) #828
Eliminated Ipython3 references #841
Fixed cookie cutter Fixes #850. #853
Removed relative imports -- fix #855. #863
Updated pytest requirement to fix issues on travis #864
Made linux compatible - travis #886
Fixed python 3.5 fails, boid failure #889, #898
Travis: Removed python 3.5 #899
Fixed example testing issues close multiprocess pools #890
Used ordered dict to make compatible with python 3.5 #892
Increased number of test to fix codecov patch #916
Fixed for #919, adding an exception for duplicate ids. #920

Batchrunner

:   -   Batch runner redux #917
    -   Fixed empty/None `variable_parameters` argument to
        BatchRunner (#861) #862
    -   Added ordereddict to BatchrunerMP for python 3.5 #893
    -   Fixed python 3.5 fails bathrunnerMP (multiple tries) #897,
        #896, #895
    -   Batchrunner_redux fixes #928

Fixed variables names, mp function locations, datacollector #933
ModularServer updated: Fix EventLoop and changes to default port #936
Ran black 20.8b1, which formats docstrings #951

0.8.7 (2020-05-05) Mammoth

Improvements

Enable BatchRunner to run specified set of parameter combinations #651 (#607)
Restructured runcontrol.js #661
Add pipenv support for mesa #678
Increase test coverage and change to codecov #692
Updates Travis to explicitly set the dist to be Xenial #699
time: Remove resolved TODO on random seed of random scheduler #708
hex_snowflake: Update description to be more informative #712
Added Coverall to Codecov in Contributing file #734
Makes opening the browser optional when launching the server #755 #754
NetworkGrid: Update to networkx 2.4 API #763
Apply black to mesa/ directory #775
Updated travis to 3.8 and updated gitignore #777
Add information (to docstring) on image as agent portrayal shape #791
Change grid empties from list to set #649 (improves speed)

Adding mypy annotation

:   -   space: Add type annotation to Grid class #779
    -   add Mypy annotation to time, agent, and model #792
    -   space: Add mypy annotation to the remaining
        methods/functions #796

Docs related

:   -   Bulk merge of docs from \'docs\' to \'master\' #684

    -

        Created useful snippets code section in the docs #668 #669

        :   -   Updating index.rst #672
            -   Clarify runserver snippet in index.rst #682

    -   Add documentation for feature (pipenv) added in #678 #683

    -

        Add docs for BatchRunner to support Variable and Fixed Parameter Contribution #679 #683

        :   -   Resources #651 in docs branch #691. This preps for
                #683 to be merged.

    -   intro tutorial: Clarify a function that is not defined in
        the class #705

    -   Updates formatting the readme Docs markdown #737

Examples related

:   -   Schelling: Separate text-only viz into run_ascii.py #706
    -   examples/Readme.md: Update description to be consistent with
        the folder names #707

Fixes

Fixes link to update code coverage module - Updates Removing last link to coveralls and replacing to codecoverage #748
Fixes D3 Network Visualization to update (rather than overwrite) #765 #767
Fix parameter order in initializing SingleGrid object #770 #769
Updating pipenv link #773
Fixed pip install from github by specifying egg #802

Compatibility fixes

:   -   Fixes VisualizationServer to be compatible with recent
        versions of Tornado #655
    -   Fixes #749 networkx incompatibility #750

Fixing typos

:   -   Fixes documentation typos in example code #695 #696
    -   Fixes typo in ModularServer\'s last parameter #711
    -   Fixed typo in BarChartModule line 100 #747
    -   Fix typo in documentation #809

Doc fixes (not relating to typos)

:   -   Update tutorial to point to correct repo location #671 #670
    -   Updating sphinx and reverting issues #674 #675 #677 #681
    -   Fixes code blocks that weren\'t showing up in the tutorial
        #686
    -   Remove figure from advanced tutorial showing the empty
        visualization #729
    -   Removes git clone from tutorial - Update intro_tutorial.rst
        #730
    -   Fixes citation links in docs tutorial section #736
    -   Fix histogram in advanced tutorial #794 #610
    -   Fixes Advanced Tutorial #elements #804 #803

Fixes to examples

:   -   Fixing test_random_walk bug - wolf sheep. #821
    -   Fixes shape_example server launch #762 #756
    -   Fixing broken table in pd_grid example #824

0.8.6 (2019-05-02) Lake Havasu City

Improvements

add docker-compose + Dockerfile support #593
install: Remove jupyter requirement #614
Add Bar and Pie Chart visualization #594 #490
Make models pickleable #582

Fixes

Year update. Happy New Year! #613
Fixed problem with grid and chart visualization javascript #612 #615
removed extra" .random" on line 178. #654
updated requirement for networkx #644 #646
Fix VisualizationServer to be compatible with recent versions of Tornado #655

0.8.5 (2018-11-26) Kearny

Improvements

Added mouse interactionHandler to close #457, fixed hexgrid drawLines #465
Run examples as part of the tests #529, #564
Add a github issue template. #560
Changes nose to pytest #561
Update and clean up cookiecutter layout #563
Updating setup to move requirements to setup.py. #566
Fixes #570 removed and updated stale comments in space.py #571
Adding model random number generator with __new__ #572
Faster agent attribute collection #576
Update install command to be edible #578
Adding read the docs yml. #579
agents can be removed and added during Scheduler.step() #584
Adding a description to bank_reserves. #587
F8 cleanup #600

Fixes

Fixes #543 (User Settable Parameters fail to work for non-string datatype #543) #544
Adding missing requirements files to examples. #550
Fixes issue #548, flockers visualization not showing up #548
updated BatchRunner (throwing error when passing in agent reporters) #556
Removing version numbers and fixing flake8 issues. #562
Fix issue #548 (Flockers visualization is not working) #566
Fixes code formatting in readmes. #577
Batchrunner.fix (BatchRunner's "variable parameters" is not strictly optional) #596

0.8.4 (2018-06-17) Jerome

Improvements

Mesa Packages docs created (#464, #480, #484, #503, #504)
Change size and tooltip text of nodes in D3 network visualization #468
Multiprocessing BatchRunner with pathos #506
Schedule.agent.dict - Implement tracking the agents in the scheduler via OrderedDict #510
Use click and add mesa run #522
Add a code of conduct #530

Fixes

iter_neighborhood() now gives correct neighborhoods for both von Neumann and Moore #459
fix typo #461
Flockers update & subsequent "F" versus "f" fix on Unix/Mac - #477, #518, #525, #500
Fixing date on release. #453
Batchrunner fixes: properly initialize models with correct parameters during subsequent runs. #486
Tornado Version Bug Fixes (upgrading #489, downgrading #497, adding to setup.py #527)
fix minor flake8 issues #519
align required dependencies between setup.py and requirements.txt #523, #528, #535
Fixes #499 grid size issue. #539

0.8.3 (2018-01-14) Hayden

Improvements

Datacollector fix #445
A first network grid model with visualization, using NetworkX and sigma.js #388
Cache pip packages for Travis setup #427
Remove localhost hardcoding + allow secure sockets #421
Update Chart.js to version 2.7.1 #401
Bank reserves example #432
Extended Grid to support hexagonal grids #409

Fixes

Faster ContinuousSpace neighbor search #439
Updating license year to 2018 #450
Updating language on license in contributing file #446
Updating license year to 2018 #450
Removed mutable defaults from DataCollector constructor #434
[BUGFIX] Torus adjustment in Grid class #429
Batchrunfixedparameters #423
[BUGFIX] Fix sidebar visibility in Edge #436
Updating Travis svg to target #master, not branches. #343
Email list language updates and link updates #399
Fix math problems in flockers; use numpy in space #378
Only start tornado ioloop if necessary #339
ContinuousSpace: Fix get_distance calculation on toroidal boundary condition #430

0.8.2 (2017-11-01) Gila Bend

Improvements

Split parameter_values into fixed & variable parameters in batchrunner #393

Fixes

Updating License year to 2017 -- very minor update #391
Flockers: fix param naming #398
Remove unused class parameters. #400
[hotfix!] Disable e2e viz test for now. #414

Fixing bug in release process. \[6a8ecb6\]

:   -   See <https://github.com/pypa/pypi-legacy/issues/670>.

0.8.1 (2017-07-03) Flagstaff (PyCon Sprints & then some)

Improvements

Bootstrap UI starter #383
Add Sugarscape Constant Growback example #385
Add best-practices document and describe models. #371

Refactored & model standards related:

:   -   Prisoner\'s Dilemma refactor to meet new model standard
        format. #377
    -   refactored boltzmann wealth model to new layout #376
    -   Update tutorial to follow new model standards #370
    -   Moving wolf sheep pngs to sub-folder for better organization
        #372
    -   Add best-practices document and describe models. #371

Modified loop over agents in schedule step method #356
Added function to use local images as shapes in GridDraw #355

Fixes

Fix math problems in flockers; use numpy in space #378
Seed both global random number generators #373, #368
Dictionary parameters fix #309
Downgrade setuptools to fix #353
Minor forest fire fix #338, #346
Allow fixed seed for replication #107
Fix tutorial and example readme for port change 8b57aa

0.8.0 (2017-01-29) - Edgar

Improvements

Updating contribution file to prevent future travis breaks #336
Updating Travis svg to target #master, not branches. #343
implement "end" message in visualization #346
Move empty-cell functions to baseclass Grid #349

Fixes

Only start tornado ioloop if necessary #339
fix boundaries of ContinousSpace #345

0.7.8.1 (2016-11-02) Duncan

Improvements

Fixes #324 -- renames all examples to be the pythonic format of naming #328
Changing to port 8521, fixes #320. #321
Opens a browser window when launching the server #323
Ticket #314 - added progress bar to BatchRunner #316
Auto update year for copyright. #329

Fixes

Minor bug fixes - Update ForestFire example notebook to new API, and rename Basic to Shape Example. #318
On-demand model stepping rather than an endless buffer #310
Updating contribution to prevent future travis breaks #330

0.7.7 (2016-08-18)

Improvements

Fixes - variable name heading0/1 in ArrowHead shape is not intuitive. #295 #301
Fixes - ArrowHead shape is not reflecting in the docs of api #300 #301
Fixes - Documentation is not reflecting latest changes wrt width-height argument order in Grid() #296 #301

0.7.6 (2016-08-13)

Theme: Scipy Sprints 2016 ( '-')人(ﾟ_ﾟ ) & Then some.

Feature adds

Add new shapes & direction indication in CanvasGrid #285
Provides support for text overlay on Circle and Rectangle shapes. #265

Improvements

Fixes Parameters of CanvasGrid(): row, col, height, width inverted #285
Fixes 'coordinates on grid are used inconsistently throughout the code' #285
Moves Agent and Model class outside of __init__.py #285
Minor pep updates to boltzmann. #269
Fix link to intro tutorial. #267
Updating template text visualization/ModularVisualization.md #273
Update intro_notebook and documents to include self.running = True in MoneyModel #275
Update .rst file location to make sure ReadTheDocs works correctly #276
Remove Mock code causing recursion and preventing build of docs. #281
MultiGrid docstring missing methods #282
No Docstring for model.grid.get_cell_list_contents #282
Refactor forest fire example #223 #288
Updating kernel version on forest fire model. #290
Making examples pep complaint. fixes #270 #291
Fixed pep8 examples and #292 #294
Fixes #283 - Fixes formatting on viz readme #299
Have Agent use self.model instead of passing it around #297

0.7.5 (2016-06-20)

Pre-sprints

Update of tutorial files and docs #176, #172
Adds np.int64() functions around some variables to get rid error caused by numpy update #188
Made examples Readme.md more readable #189

From PyCon Sprints

Updating model example readmes #207
Added nose to requirements #208
Updated link on style google style guide #209
Reset visualization when websocket connection is opened #210
Remove unused scipy dependency #211
Introduce a requirements.txt for the tutorial. #212
Remove references to running in tutorial #213
Simplify travis.yml; add python versions #215
Update Flocker Readme.md #216
Syntax error in .rst was swallowing a code block #217
Fixup HistogramModule in the tutorial. #218
add more test coverage to time #221
add a requirements.txt for WolfSheep. #222
add a requirements.txt for Schelling. #224
Refactor color patches example #227
Ignored _build sphinx docs still in repo #228
Intro Tut completely in ipynb #230
pass optional port parameter to ModularServer.launch #231
open vis immediately when running color patches #232
Adds .DS_store to .gitignore #237
Documentation Update #240
Small fix for reading links #241
Test batchrunner #243
clean up TextVisualization #245
Documentation Update #250
Update Game of Life example to new format #253
Update Flockers example to new format #254
Update Epstein model to new layout #255
Subclassing object is unnecessary in Python 3 #258

Post PyCon Sprints

Adds a copy of jquery directly into the code. #261

0.7.0 (2016-03-06)

#184 Adding terminal echo for server launch to signal person running the model
#183 Adding Conway's Game of Life simulation to the examples.

0.6.9 (2016-02-16)

#170 Adding multi-stage activation
#169 Wolf-Sheep Cleanup
Updates requirements to latest libraries

0.6.7 (2015-07-11)

Improvements

Allow cell_list_content methods in Grids to accept single tuples in addition to lists

0.6.6 (2015-07-11)

Theme: Scipy Sprints ( '-')人(ﾟ_ﾟ )

Improvements

Standardizes the arguments passed to spatial functions to only tuples, not separate x and y coordinates. (Breaks backwards compatibility)

0.6.5.1 (2015-07-11) ++++++++++++++++++

Theme: Scipy Sprints ( '-')人(ﾟ_ﾟ )

Improvements

Adding version, license, copyright, title to __init__.py
Auto updating version in setup.py

Fixes

Updating MANIFEST.in to include visualization templates that were missing.

0.6.5 (2015-07-11)

Theme: Scipy Sprints ( '-')人(ﾟ_ﾟ )

Edits

Additions to tutorial doc
Minor edits to README & Intro
Minor edits / clean up to setup.py
Removing .ipynb_checkpoints
Removing out-of-date planning documentation.

Fixes

Use setuptools' find_packages function to get the list of packages to install, fixes #141

Improvements

Use package_data for include the web files
Use a MANIFEST.in file to include the LICENSE file in source distributions
Using conda on Travis allows much faster builds and test runs

0.6.2 (2015-07-09)

Improvement: Adding continuous space.
Improvement: Adding a simultaneous activation scheduler.

New models:

:   -   Flockers
    -   Spatial Demographic Prisoner\'s Dilemma (PD_Grid)

0.6.1 (2015-06-27)

Fixes: Order of operations reversed: agent is removed first and then it is placed.
Improvement: LICENSE_ was updates from MIT to Apache 2.0.

0.6.0 (2015-06-21)

Improvement: Add modular server feature, which breaks up a model into a .py file and a .js file. This breaks backwards compatibility.

Pre 0.6.0

Code that is pre-0.6.0 is very unstable.

Our initial release was 0.5.0 (2014-11).

It included code for placing agents on a grid; a data collector and batch runner; and a front-end visualization using HTML 5 and JavaScript.

General

Objects create -- Agent, Time, Space
Project moved to Python 3
Tornado server setup

Front-end

Front-end grid implemented
ASCII visualization implemented

Examples models

Forest Fire
Schelling
Wolf-Sheep Predation

0.1.0 (2014-09-19)

A conversation
Birth

FilesExpand file tree

HISTORY.md

Latest commit

History

HISTORY.md

File metadata and controls

title: Release History

3.5.0 (2026-02-15)

Highlights

Public event scheduling and time advancement

Stabilized event scheduling system

Deprecations toward Mesa 4.0

Internal architecture improvements

New agent creation from DataFrames

Experimental features

Scenarios

Reactive model and data collection

What's Changed

⏳ Deprecations

🎉 New features added

🛠 Enhancements made

🧪 Experimental features

🐛 Bugs fixed

🔍 Examples updated

📜 Documentation improvements

🔧 Maintenance

New Contributors

3.4.2 (2026-01-23)

Highlights

What's Changed

🐛 Bugs fixed

📜 Documentation improvements

3.4.1 (2026-01-10)

Highlights

What's Changed

🛠 Enhancements made

🐛 Bugs fixed

🔍 Examples updated

📜 Documentation improvements

🔧 Maintenance

New Contributors

3.4.0 (2025-12-24)

Highlights

Universal simulation time with model.time

Improved batch run reproducibility

Strengthened deprecation policy

Organization name change

Python 3.12+ required

Other improvements

What's Changed

⏳ Deprecations

🎉 New features added

🛠 Enhancements made

🐛 Bugs fixed

🔍 Examples updated

📜 Documentation improvements

🔧 Maintenance

New Contributors

3.3.1 (2025-11-07)

Highlights

What's Changed

🐛 Bugs fixed

🔍 Examples updated

📜 Documentation improvements

🔧 Maintenance

New Contributors

3.3.0 (2025-09-06)

Highlights

What's Changed

🧪 Experimental features

🎉 New features added

🛠 Enhancements made

🐛 Bugs fixed

📜 Documentation improvements

🔧 Maintenance

Other changes

New Contributors

3.2.0 (2025-05-04)

Highlights

Stabilization of Discrete Space

Universal simulation time with `model.time`