Drop Python 3.11, require Python 3.12+ and update to modern type parameter syntax (#2842)

* Drop Python 3.11, require Python 3.12+, test Python 3.14

This commit drops Python 3.11 support and require Python 3.12+ following SPEC 0.

See the Python 3.12 release notes: https://docs.python.org/3/whatsnew/3.12.html

The Mesa 3.3.x release series will keep supporting Python 3.11.

* Upgrade to Python 3.12 and apply type parameter syntax

With the minimum Python version now at 3.12, we can use the modern type parameter syntax (PEP 695) instead of the legacy Generic[T] pattern. This change improves code readability and aligns with current Python typing best practices.

Changes:
- CellCollection: Convert from Generic[T] to type parameter syntax with Cell bound
- DiscreteSpace: Convert from Generic[T] to type parameter syntax with Cell bound
- Grid: Remove redundant Generic[T] inheritance (already inherits from DiscreteSpace[T])
- accept_tuple_argument: Convert function type variable to use type parameter syntax
- Remove unused Generic imports from typing module

These changes are purely syntactic modernizations with no functional impact. The type parameter syntax is more concise and better integrated with Python's type system.

Fixes ruff UP046 and UP047 violations.

* Remove redundant Generic inheritance from Grid class

The Grid class inherits from DiscreteSpace[T], which already provides generic type support. The additional Generic[T] inheritance is redundant and triggers a ruff UP046 violation.

Changes:
- Remove Generic[T] from Grid class inheritance
- Remove unused Generic import from typing module
- Keep TypeVar T definition as it's still needed for DiscreteSpace[T] parameterization

Fixes ruff UP046 violation in grid.py.

* CI: Remove Python 3.11 run

Author: EwoutH

.github/workflows/build_lint.yml

@@ -35,8 +35,6 @@ jobs:
         include:
           - os: ubuntu
             python-version: "3.12"
-          - os: ubuntu
-            python-version: "3.11"
           # Disabled for now. See https://github.com/projectmesa/mesa/issues/1253
           #- os: ubuntu
           #  python-version: 'pypy-3.8'

.pre-commit-config.yaml

@@ -17,7 +17,7 @@ repos:
     rev: v3.20.0
     hooks:
     -   id: pyupgrade
-        args: [--py311-plus]
+        args: [--py312-plus]
 -   repo: https://github.com/pre-commit/pre-commit-hooks
     rev: v6.0.0  # Use the ref you want to point at
     hooks:

docs/tutorials/0_first_model.ipynb

@@ -53,7 +53,7 @@
    "source": [
     "### Tutorial Setup\n",
     "\n",
-    "Create and activate a [virtual environment](http://docs.python-guide.org/en/latest/dev/virtualenvs/). *Python version 3.11 or higher is required*.\n",
+    "Create and activate a [virtual environment](http://docs.python-guide.org/en/latest/dev/virtualenvs/). *Python version 3.12 or higher is required*.\n",
     "\n",
     "Install Mesa:\n",
     "\n",

mesa/discrete_space/cell_collection.py

@@ -20,7 +20,7 @@
 from collections.abc import Callable, Iterable, Mapping
 from functools import cached_property
 from random import Random
-from typing import TYPE_CHECKING, Generic, TypeVar
+from typing import TYPE_CHECKING, TypeVar
 
 if TYPE_CHECKING:
     from mesa.discrete_space.cell import Cell
@@ -29,7 +29,7 @@
 T = TypeVar("T", bound="Cell")
 
 
-class CellCollection(Generic[T]):
+class CellCollection[T: Cell]:
     """An immutable collection of cells.
 
     Attributes:

mesa/discrete_space/discrete_space.py

@@ -18,7 +18,7 @@
 import warnings
 from functools import cached_property
 from random import Random
-from typing import Generic, TypeVar
+from typing import TypeVar
 
 from mesa.agent import AgentSet
 from mesa.discrete_space.cell import Cell
@@ -27,7 +27,7 @@
 T = TypeVar("T", bound=Cell)
 
 
-class DiscreteSpace(Generic[T]):
+class DiscreteSpace[T: Cell]:
     """Base class for all discrete spaces.
 
     Attributes:

mesa/discrete_space/grid.py

@@ -17,7 +17,7 @@
 from collections.abc import Sequence
 from itertools import product
 from random import Random
-from typing import Any, Generic, TypeVar
+from typing import Any, TypeVar
 
 from mesa.discrete_space import Cell, DiscreteSpace
 from mesa.discrete_space.property_layer import (
@@ -56,7 +56,7 @@ def unpickle_gridcell(parent, fields):
     return instance
 
 
-class Grid(DiscreteSpace[T], Generic[T], HasPropertyLayers):
+class Grid(DiscreteSpace[T], HasPropertyLayers):
     """Base class for all grid classes.
 
     Attributes:

mesa/space.py

@@ -61,7 +61,7 @@
 F = TypeVar("F", bound=Callable[..., Any])
 
 
-def accept_tuple_argument(wrapped_function: F) -> F:
+def accept_tuple_argument[F: Callable[..., Any]](wrapped_function: F) -> F:
     """Decorator to allow grid methods that take a list of (x, y) coord tuples to also handle a single position.
 
     Tuples are wrapped in a single-item list rather than forcing user to do it.

pyproject.toml

@@ -6,7 +6,7 @@ build-backend = "hatchling.build"
 name = "Mesa"
 description = "Agent-based modeling (ABM) in Python"
 license = { text = "Apache 2.0" }
-requires-python = ">=3.11"
+requires-python = ">=3.12"
 authors = [
   { name = "Project Mesa Team", email = "[email protected]" },
 ]
@@ -25,7 +25,6 @@ classifiers = [
   "Topic :: Scientific/Engineering :: Artificial Intelligence",
   "Intended Audience :: Science/Research",
   "Programming Language :: Python :: 3 :: Only",
-  "Programming Language :: Python :: 3.11",
   "Programming Language :: Python :: 3.12",
   "Programming Language :: Python :: 3.13",
   "License :: OSI Approved :: Apache Software License",
@@ -98,9 +97,9 @@ path = "mesa/__init__.py"
 
 [tool.ruff]
 # See https://github.com/charliermarsh/ruff#rules for error code definitions.
-# Hardcode to Python 3.11.
+# Hardcode to Python 3.12.
 # Reminder to update mesa-examples if the value below is changed.
-target-version = "py311"
+target-version = "py312"
 extend-exclude = ["build"]
 
 [tool.ruff.lint]