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pythonpython-typingunion-types
Cos
Cos

Reputation: 562

Python typing.get_args and typing.Union

I'm unable to get any information about the parameter when using typing.Union:

import typing

x = typing.Union[str,int]
print(typing.get_args(x))

Output: (<class 'str'>, <class 'int'>)

def f(y: typing.Union[str,int]):
    print(typing.get_args(y))

f(1)

Output: ()

Upvotes: 0

Views: 1269

Answers (2)

Paweł Rubin
Paweł Rubin

Reputation: 3360

You can use typing.get_type_hints() to get type annotations of f:

def f(y: typing.Union[str,int]):
    print(typing.get_type_hints(f))

f(1)

Upvotes: 0

Daniil Fajnberg
Daniil Fajnberg

Reputation: 18458

x is a union of types. y is of the union type (i.e. either of type int or of type str).

Try print(type(x)) and print(type(y)).

In your function signature, you merely annotated that y should be either of type str or of type int. So you'll be calling get_args on an int, when you pass 1 to the function.

x in your code is just an alias for that type union object.

In fact, you could do this:

from typing import Union

x = Union[str, int]

def f(y: x):
    ...

This is equivalent:

from typing import Union

def f(y: Union[str, int]):
    ...

Upvotes: 1

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