You can do that with literal types. from typing_extensions import Literal # from typing import Literal # Python 3.8 or higher def fun(b: int) -> Literal[“a”, “b”, “c”]: if b == 0: return “a” if b == 1: return “b” return “d” mypy is able to detect the return “d” as a invalid statement: error: … Read more
Typed argument parser was made for exactly this purpose. It wraps argparse. Your example is implemented as: from tap import Tap class ArgumentParser(Tap): somearg: str parsed = ArgumentParser().parse_args([‘–somearg’, ‘someval’]) the_arg = parsed.somearg Here’s a picture of it in action. It’s on PyPI and can be installed with: pip install typed-argument-parser Full disclosure: I’m one of … Read more
I was looking for something similar and found the library typeguard. This can automatically do runtime type checks wherever you want. Checking types directly as in the question is also supported. From the docs, from typeguard import check_type # Raises TypeError if there’s a problem check_type(‘variablename’, [1234], List[int])
Type hints are entirely meant to be ignored by the Python runtime, and are checked only by 3rd party tools like mypy and Pycharm’s integrated checker. There are also a variety of lesser known 3rd party tools that do typechecking at either compile time or runtime using type annotations, but most people use mypy or … Read more
You can’t use Callable to say anything about additional arguments; they are not generic. Your only option is to say that your decorator takes a Callable and that a different Callable is returned. In your case you can nail down the return type with a typevar: RT = TypeVar(‘RT’) # return type def inject_user() -> … Read more
Since Python 3.5 you may use typing module. Quoting docs, A type alias is defined by assigning the type to the alias: Vector = List[float] To learn more about enforcing types in Python you may want to get familiar with PEPs: PEP483 and PEP484. Python historically was using duck-typing instead of strong typing and hadn’t … Read more
You’re looking for types.ModuleType.
You want a type union. For Python 3.10+: def post_xml(data: str | ET.Element): For earlier versions: from typing import Union def post_xml(data: Union[str, ET.Element]): …
You have a forward declaration; functions (to be bound as methods) are created before the class is, so the name Vector doesn’t yet exist. Only when all of the class body has been executed, can Python create the class object and bind the name Vector to it. Simply use a string with the name instead: … Read more
As pointed out by Blckknght, you and Stanislav Ivanov in the comments, you can use NamedTuple: from typing import NamedTuple class NameInfo(NamedTuple): name: str first_letter: str def get_info(name: str) -> NameInfo: return NameInfo(name=name, first_letter=name[0]) Starting from Python 3.8 you can use TypedDict which is more similar to what you want: from typing import TypedDict class … Read more