|
| 1 | +--- |
| 2 | +title: Strict Typing in Python |
| 3 | +--- |
| 4 | + |
| 5 | +import Tabs from '@theme/Tabs'; |
| 6 | +import TabItem from '@theme/TabItem'; |
| 7 | + |
| 8 | +# Overview |
| 9 | + |
| 10 | +This guide explains how to use Python's type system effectively with the Infrahub SDK, focusing on the use of Protocols for type-safe development. |
| 11 | + |
| 12 | +:::note What is Python Typing |
| 13 | + |
| 14 | +Python typing allows you to specify the expected data types of variables, function arguments, and return values to improve code clarity and catch bugs early. |
| 15 | + |
| 16 | +```python |
| 17 | +# Basic type hints |
| 18 | +def percentage(num1: int, num2: int) -> float: |
| 19 | + return (num1 / num2) * 100 |
| 20 | +``` |
| 21 | + |
| 22 | +::: |
| 23 | + |
| 24 | +## Leveraging Python protocols |
| 25 | + |
| 26 | +The Python SDK for Infrahub has been designed to automatically work with any schemas loaded into Infrahub. |
| 27 | +Internally, the Python SDK generates dynamic Python representations of your schemas. |
| 28 | + |
| 29 | +While this approach improves code readability, it presents challenges with type checking because each object has a different signature based on your schema. |
| 30 | + |
| 31 | +### Without protocols |
| 32 | + |
| 33 | +In the example below, type checkers like Mypy will typically complain about `blue_tag.description.value` because `description` is a dynamic parameter generated by the SDK. |
| 34 | + |
| 35 | +```python |
| 36 | +# Type checker cannot verify the existence of 'description' |
| 37 | +blue_tag = client.get("BuiltinTag", name__value="blue") # blue_tag is of type InfrahubNode or InfrahubNodeSync |
| 38 | +blue_tag.description.value = "The blue tag" # Mypy: error: "InfrahubNode" has no attribute "description" |
| 39 | +blue_tag.save() |
| 40 | +``` |
| 41 | + |
| 42 | +### With protocols |
| 43 | + |
| 44 | +To provide strict type checking while maintaining platform extensibility, the Python SDK integrates with Python Protocols. |
| 45 | + |
| 46 | +For all core and internal models, the protocols are included in the SDK under `infrahub_sdk.protocols`. |
| 47 | +Whenever you need to specify the kind of object you're working with as a string, you can use the corresponding protocol instead. |
| 48 | + |
| 49 | +```python |
| 50 | +from infrahub_sdk.protocols import BuiltinTag |
| 51 | + |
| 52 | +# Type checker can now verify all attributes |
| 53 | +blue_tag = client.get(BuiltinTag, name__value="blue") # blue_tag is of type BuiltinTag |
| 54 | +blue_tag.description.value = "The blue tag" # No type errors |
| 55 | +blue_tag.save() |
| 56 | +``` |
| 57 | + |
| 58 | +:::note Python Protocols |
| 59 | + |
| 60 | +Python Protocols, introduced in PEP 544, define a set of method and property signatures that a class must implement to be considered a match, enabling structural subtyping (also known as "duck typing" with static checks). They allow you to specify behavior without requiring inheritance, making code more flexible and type-safe. |
| 61 | + |
| 62 | +More information about Python Protocols can be found [here](https://typing.python.org/en/latest/spec/protocol.html) |
| 63 | + |
| 64 | +::: |
| 65 | + |
| 66 | +## Generating custom protocols based on your schema |
| 67 | + |
| 68 | +You can generate Python Protocols for your own models using the `infrahubctl protocols` command. This supports both synchronous and asynchronous Python code. |
| 69 | + |
| 70 | +It's possible to provide the schema from a local directory or from an existing Infrahub Instance. |
| 71 | + |
| 72 | +<Tabs groupId="local-remote"> |
| 73 | + <TabItem value="Existing Infrahub Instance" default> |
| 74 | + |
| 75 | + ```shell |
| 76 | + export INFRAHUB_ADDRESS=https://infrahub.example.com |
| 77 | + infrahubctl protocols --out lib/protocols.py --sync |
| 78 | + ``` |
| 79 | + |
| 80 | + </TabItem> |
| 81 | + <TabItem value="Local Directory" default> |
| 82 | + |
| 83 | + ```shell |
| 84 | + infrahubctl protocols --schemas schemas/tag.schema.yml --out lib/protocols.py |
| 85 | + ``` |
| 86 | + |
| 87 | + </TabItem> |
| 88 | +</Tabs> |
| 89 | + |
| 90 | +> When using a local directory, Protocols for Profiles and Object Templates won't be generated. |
| 91 | +
|
| 92 | +## Using custom protocols |
| 93 | + |
| 94 | +After generation, you can import and use your custom protocols as describe below. |
| 95 | + |
| 96 | +```python |
| 97 | +from lib.protocols import MyOwnObject |
| 98 | + |
| 99 | +# Use your custom protocol |
| 100 | +my_object = client.get(MyOwnObject, name__value="example") |
| 101 | +``` |
| 102 | + |
| 103 | +> if you don't have your own Python module, it's possible to use relative path by having the `procotols.py` in the same directory as your script/transform/generator |
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