Python 打字：字面量

Question

I am writing a function that takes an argument dtype of type type as shown below.

def my_function(dtype: type):
    pass

Is there a way to restrict the value of dtype only to str and int ? The type union str | int str | int will not do the job because it will then be interpreted as dtype can have a value with type str or int , which is not the case.

Also, I may not want to assert the value of dtype because mypy doesn't seem to work well with it.

def my_function(dtype: type):
    assert dtype == str or dtype == int

Is there a workaround to this problem?

Answer 1

Ok, I'm going to post the answer for future reference. Big thank you to juanpa.arrivillaga for the solution!

We can use the genericType[T] from the typing module to refer to a literal type, as shown below.

from typing import Type


def my_function(dtype: Type[str] | Type[int]):
    pass

Or from Python 3.9 , builtins.type now supports the type[T] generic, as stated in PEP 585 .

def my_function(dtype: type[str] | type[int]):
    pass