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Should we use _ProtocolMeta in typing.py? #8998

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Should we use _ProtocolMeta in typing.py?#8998

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@sobolevn
sobolevn
opened on Oct 27, 2022

Right now _ProtocolMeta is never used:

typeshed/stdlib/typing.pyi

Line 282 in 739711e

class _ProtocolMeta(ABCMeta): ...

But, it is a base metaclass for Protocol type in typing.py: https://github.com/python/cpython/blame/723ebe76e787cfa6b08cc9587dd679f3234a1025/Lib/typing.py#L1965

It is also used for all Protocol types (we currently just use ABCMeta for them`):

typeshed/stdlib/typing.pyi

Lines 287 to 305 in 739711e

@runtime_checkable
class SupportsInt(Protocol, metaclass=ABCMeta):
@abstractmethod
def __int__(self) -> int: ...
@runtime_checkable
class SupportsFloat(Protocol, metaclass=ABCMeta):
@abstractmethod
def __float__(self) -> float: ...
@runtime_checkable
class SupportsComplex(Protocol, metaclass=ABCMeta):
@abstractmethod
def __complex__(self) -> complex: ...
@runtime_checkable
class SupportsBytes(Protocol, metaclass=ABCMeta):
@abstractmethod
def __bytes__(self) -> bytes: ...

CPython: https://github.com/python/cpython/blame/723ebe76e787cfa6b08cc9587dd679f3234a1025/Lib/typing.py#L2745

So, the question is:

  1. Should we use for Protocol class? It is rather complex, because right now Protocol is _SpecialForm
  2. Should we use it for Protocol types in typing.pyi?

Activity

  1. JelleZijlstra commented on Oct 27, 2022

    @JelleZijlstra
    JelleZijlstra
    on Oct 27, 2022
    Member

    typing.pyi is central to type checking and typecheckers need to heavily special case for the contents of the stub. Therefore, I think we should only make changes here if they fix a concrete problem for users, not out of mere perfectionism.

  2. sobolevn
    closed this as completedon Oct 28, 2022
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