New submission from conchylicultor <etiennefg....@gmail.com>:
Currently, because `BinaryIO` is subclass of `IO[bytes]`, the 2 cannot be used
interchangeably.
Example with pytype:
```
def iter_zip(arch_f) -> List[typing.BinaryIO]]:
with open(arch_f, 'rb') as fobj:
z = zipfile.ZipFile(fobj)
return [z.open(member) for member in z.infolist()]
```
Raise:
```
Expected: Tuple[str, BinaryIO]
Actually returned: Tuple[Any, IO[bytes]]
```
Technically pytype is right as `ZipFile.open() -> IO[bytes]`:
https://github.com/python/typeshed/blob/ca45cb21a8a0422cbb266cb25e08051fe481887c/stdlib/2and3/zipfile.pyi#L109
But this makes BinaryIO usage quite confusing.
>From the implementation, it seems that the BinaryIO is slightly different
>(https://github.com/python/cpython/blob/9f004634a2bf50c782e223e2eb386ffa769b901c/Lib/typing.py#L2094):
But the documentation is unclear about the difference between the 2
https://docs.python.org/3/library/typing.html#typing.BinaryIO
Additionally, `typing.IO` is implemented as Generic but shouldn't this be a
Protocol instead ?
----------
messages: 382143
nosy: conchylicultor
priority: normal
severity: normal
status: open
title: Confusing that BinaryIO and IO[bytes] cannot be used interchangeably
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Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue42512>
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