Python void return type annotation

Question

In python 3.x, it is entirely expected to utilize return type explanation of a capacity/function, for example, 

def foo() -> str:

    return "bar"

What is the right explanation for the "void" type?

I'm considering these three options:

def foo() -> None:

• not logical IMO, because None is not a type,

def foo() -> type(None):

• using the best syntax I know for obtaining NoneType,

def foo():

• omit explicit return type information.

Choice 2. appears to be the most consistent to me, however, I've effectively seen a few occurrences of 1.

        

Answer 1

This is directly from PEP 484 - Type Hints documentation: 

When used in a type hint, the expression None is considered equivalent to type(None).

Also, as you can see the majority of the models utilize None as bring type back.     

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