type annotations: Replace Union[a, b] with a | b, Optional[a] with a | None #1341

[Aryan1Mahahjan]

Solving the issue of replacing Union[a, b] with a | b and Optional[a] with a | None in type annotations:

Replacing Union[a, b] with a | b:

Improves readability and clarity of type hints. Makes it easier to understand what types are allowed for a variable or function parameter. Provides better type checking by the static type checker.

It may CI issuse in build / build (ubuntu, 3.9) (pull_request)

Aryan1Mahajahn

[github-actions[bot]]

Performance benchmarks:

Model	Size	Init time [95% CI]	Run time [95% CI]
Schelling	small	🔵 -1.3% [-1.6%, -1.1%]	🔵 -0.7% [-0.9%, -0.6%]
Schelling	large	🔵 -0.2% [-0.7%, +0.2%]	🔵 -0.6% [-2.6%, +1.4%]
WolfSheep	small	🔵 +1.7% [+1.4%, +2.1%]	🔵 -1.5% [-1.6%, -1.4%]
WolfSheep	large	🔵 +3.4% [+0.8%, +5.8%]	🔵 +1.7% [+1.0%, +2.4%]
BoidFlockers	small	🔵 +3.5% [+2.5%, +4.4%]	🔵 -0.8% [-1.6%, +0.0%]
BoidFlockers	large	🔴 +4.4% [+3.9%, +4.8%]	🔵 -1.6% [-2.1%, -1.2%]

[rht]

Now we just have to wait until we drop Python 3.9 support. I think that will happen after the Mesa 2.3 release, which will probably release in February or March. If you want, you can help with that when the time comes.

What's blocking us from doing it for Mesa 2.3? See also https://github.com/projectmesa/mesa/pull/1756#discussion_r1368411042.

[Aryan1Mahahjan]

Hi, is there any way I can contribute in any similar issue.

[EwoutH]

I think improving the example models in Mesa-examples and adding new ones is now the most useful. Especially if you include new features like the AgentSet or PropertyLayer.

[rht]

Adding more Mypy annotations would also be useful.

[rht]

@Aryan1Mahahjan here are several type checking errors for mesa/agent.py

mesa/agent.py:45: error: Type argument "float" of "NDArray" must be a subtype of "generic"  [type-var]
mesa/agent.py:79: error: "Model" has no attribute "random"  [attr-defined]
mesa/agent.py:139: error: Argument 1 of "__contains__" is incompatible with supertype "AbstractSet"; supertype defines the argument type as "object"  [override]
mesa/agent.py:139: note: This violates the Liskov substitution principle
mesa/agent.py:139: note: See https://mypy.readthedocs.io/en/stable/common_issues.html#incompatible-overrides
mesa/agent.py:139: error: Argument 1 of "__contains__" is incompatible with supertype "Sequence"; supertype defines the argument type as "object"  [override]
mesa/agent.py:139: error: Argument 1 of "__contains__" is incompatible with supertype "Container"; supertype defines the argument type as "object"  [override]
mesa/agent.py:200: error: "WeakKeyDictionary[Agent, None]" has no attribute "data"  [attr-defined]
mesa/agent.py:279: error: Signature of "__getitem__" incompatible with supertype "Sequence"  [override]
mesa/agent.py:279: note:      Superclass:
mesa/agent.py:279: note:          @overload
mesa/agent.py:279: note:          def __getitem__(self, int, /) -> Any
mesa/agent.py:279: note:          @overload
mesa/agent.py:279: note:          def __getitem__(self, slice, /) -> Sequence[Any]
mesa/agent.py:279: note:      Subclass:
mesa/agent.py:279: note:          def __getitem__(self, int | slice, /) -> Agent
mesa/agent.py:289: error: Incompatible return value type (got "Agent | list[Agent]", expected "Agent")  [return-value]
mesa/agent.py:359: error: "Model" has no attribute "random"  [attr-defined]

are you interested in looking to fixing it? You should start with opening a PR with small changes first, so that it can get merged earlier.

[Aryan1Mahahjan]

Yes I am interested I will look into it.

[Aryan1Mahahjan]

It works on my machine no errors found

[rht]

You do type checking by installing Mypy and running mypy <the file.py> or mypy thedirectory/.