I wonder how to make this getter more type-safe: VALUES = { '1': 'One', '2': 'Two', '3': 'Three' } def get(key : str) -> str: return VALUES[key] Instead of the type str I would love to ha...

When speaking about Generics, Python gives the following example: from collections.abc import Sequence from typing import TypeVar T = TypeVar('T') # Declare type variable def first(l: Sequence[T]...

I would like to instantiate a typing Union of two classes derived from pydantic.BaseModel directly. However I get a TypeError: Cannot instantiate typing.Union. All examples I have seen declare Unio...

I'm having a hard time understanding from the documentation exactly what typing.Annotated is good for and an even harder time finding explanations/examples outside the documentation. Or does it &qu...

My code looks something like this, which runs fine BDW without any errors from typing import Literal def verify(word: str) -> Literal['Hello XY']: a = 'Hello ' + word return a a = verify('XY...

So, I was writing an event emitter class using Python. Code currently looks like this: from typing import Callable, Generic, ParamSpec P = ParamSpec('P') class Event(Generic[P]): def __init__(se...

Based on the documentation for Python Typing, these are the ones that deal with Tuples... Tuple[()] - empty tuple Tuple[int, int] - tuple of two int objects Tuple[int, ...] - tuple of an arbitrar...

a variable annotated with Type[C] may accept values that are classes themselves How do you do this with TypeVarTuples (PEP 646) from typing import TypeVar, TypeVarTuple T = TypeVar("T") ...

This doesn't seem to work: from typing import NewType MyStr = NewType("MyStr", str) x = MyStr("Hello World") isinstance(x, MyStr) I don't even get False, but TypeError: isins...

Say you want to wrap the dataclass decorator like so: from dataclasses import dataclass def something_else(klass): return klass def my_dataclass(klass): return something_else(dataclass(klass)) ...

How can I specify one type for all of these callables: a(str) b(str, str) c(str, str, str) d(str, str, str, str) I found that I can specify Callable[..., None] in a general way, but how to specify...

I have the following in test.py: def f(x: int) -> float: pass if __name__=="__main__": f(4) When I run mypy --strict test.py, I get no errors. I expected mypy would be able to infe...

My type annotations I currently have look similar to the following, and I want to use an typing alias to not repeat myself so much: A class has class variables, which can be either: some specified...

Python's PEP 544 introduces typing.Protocol for structural subtyping, a.k.a. "static duck typing". In this PEP's section on Merging and extending protocols, it is stated that The general...

How can I automatically create the boilerplate code of pyi files? I want to create a pyi file for type hinting as described in pep484 which contains all method names. I don't want magic. I want to ...

I'm trying to use mypy in my projects, but many of the instance attributes I use are only initialized after __init__, and not inside it. However, I do want to keep the good practice of declaring al...

Assume you have a Python class that inherits from Generic[T]. Is there any way to get a hold of the actual type passed in from within the class/instance? For example, from typing import TypeVar, Ty...

Function Annotations: PEP-3107 Background: I am PyCharm user w/CPython 3.4x on Linux. I find it helps to annotate function parameters and return types. The IDE can better hint when I use these meth...

I am trying to import ArrayLike doing from numpy.typing import ArrayLike, and I get the error mentioned in the title: ModuleNotFoundError: No module named 'numpy.typing' I know I could simply write...

I want to add typing to a Python function that takes in a type as an argument (actually, a subtype of a specific class), and return an instance of that type. Think a factory that takes in the speci...

I'm unsure of the Python convention for type hinting instance variables - I've been doing them within the __init__ constructor arguments like seen here: class LoggedVar(Generic[T]): def __init__(s...

Consider a function that performs type promotion, e.g. a simple multiplication of two numbers that can both be either int or float: def mul(a: int | float, b: int | float): # return type? return a...

In the Indirect parametrization example I want to type hint request.param indicating a specific type, a str for example. The problem is since the argument to fixt must be the request fixture there ...

Python 3.12 has the type statement. How do I document the type alias properly? I tried: type Number = int | float """Represents a scalar number that is either an integer or float&quo...

Say we have a function, for instance reduce, that takes in a callback, for instance combiner. If I have an example callback function, exampleReducer, I would like to avoid having to write the type ...