Handle special object NotImplemented like type (like it done for None) #742

penguinolog · 2020-07-22T07:33:59Z

Currently incorrect, but useful to be supported:

def fun() -> Union[bool, NotImplemented]: ...

This will better explain expected, than:

def fun() -> Union[bool, Any]: ...

gvanrossum · 2020-07-22T13:51:08Z

What’s a realistic use case?

penguinolog · 2020-07-22T14:50:52Z

Real use-cases: mainly reversible operations, where NotImplemented cause reverse operation (__add__ -> __radd__ and etc)

gvanrossum · 2020-07-22T15:03:14Z

Okay, this makes sense (maybe I would have understood if you had provided an example where this actually makes sense, like

class Num:
    def __add__(self, other: Any) -> Union[Num, NotImplemented]:
        if not isinstance(other, Num):
            return NotImplemented
        <add two Nums>

penguinolog changed the title ~~Threaten special NotImplemented object like type (like it done for None)~~ Handle special object NotImplemented like type (like it done for None) Jul 22, 2020

python / typing

Handle special object NotImplemented like type (like it done for None) #742

Handle special object NotImplemented like type (like it done for None) #742

penguinolog commented Jul 22, 2020

gvanrossum commented Jul 22, 2020

penguinolog commented Jul 22, 2020

gvanrossum commented Jul 22, 2020

python / typing

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Handle special object NotImplemented like type (like it done for None) #742

Handle special object NotImplemented like type (like it done for None) #742

Comments

penguinolog commented Jul 22, 2020

gvanrossum commented Jul 22, 2020

penguinolog commented Jul 22, 2020

gvanrossum commented Jul 22, 2020

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