Optional callable raises TypeError

[ofek]

BPO	42965
Nosy	@ofek, @Fidget-Spinner

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2021-01-19.14:48:11.240>
created_at = <Date 2021-01-19.08:11:26.387>
labels = ['type-bug', 'library', '3.9']
title = 'Optional callable raises TypeError'
updated_at = <Date 2021-01-19.14:48:11.239>
user = 'https://github.com/ofek'

bugs.python.org fields:

activity = <Date 2021-01-19.14:48:11.239>
actor = 'Ofekmeister'
assignee = 'none'
closed = True
closed_date = <Date 2021-01-19.14:48:11.240>
closer = 'Ofekmeister'
components = ['Library (Lib)']
creation = <Date 2021-01-19.08:11:26.387>
creator = 'Ofekmeister'
dependencies = []
files = []
hgrepos = []
issue_num = 42965
keywords = []
message_count = 4.0
messages = ['385246', '385247', '385262', '385264']
nosy_count = 2.0
nosy_names = ['Ofekmeister', 'kj']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue42965'
versions = ['Python 3.9']

[ofek]

https://docs.python.org/3.9/library/typing.html#callable

Python 3.9.1 (default, Jan 12 2021, 16:45:25)
[GCC 8.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from typing import Optional
>>> from collections.abc import Callable
>>>
>>> Hasher = Optional[Callable[[bytes], bytes]]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.9/typing.py", line 262, in inner
    return func(*args, **kwds)
  File "/usr/local/lib/python3.9/typing.py", line 339, in __getitem__
    return self._getitem(self, parameters)
  File "/usr/local/lib/python3.9/typing.py", line 463, in Optional
    return Union[arg, type(None)]
  File "/usr/local/lib/python3.9/typing.py", line 262, in inner
    return func(*args, **kwds)
  File "/usr/local/lib/python3.9/typing.py", line 339, in __getitem__
    return self._getitem(self, parameters)
  File "/usr/local/lib/python3.9/typing.py", line 451, in Union
    parameters = _remove_dups_flatten(parameters)
  File "/usr/local/lib/python3.9/typing.py", line 231, in _remove_dups_flatten
    return tuple(_deduplicate(params))
  File "/usr/local/lib/python3.9/typing.py", line 205, in _deduplicate
    all_params = set(params)
TypeError: unhashable type: 'list'
>>>
>>> from typing import Tuple
>>> Hasher = Optional[Callable[Tuple[bytes], bytes]]
>>>

Tuple type for arguments makes it work

[ofek]

I'm using the deprecated typing.Callable instead now and that works

[Fidget-Spinner]

Hello, this issue is a byproduct of bpo-42195. It has already been fixed on Python 3.10, and on Python 3.9.2 (which isn't out yet). You can see the what's new for it here https://docs.python.org/3/whatsnew/3.9.html#notable-changes-in-python-3-9-2.

The expected release date for Python 3.9.2 is Monday, 2021-02-15 according to PEP-596 https://www.python.org/dev/peps/pep-0596/.

For now, I guess you'll have to use the old typing.Callable, then update it in newer versions of Python.

On Python 3.10a4:
>>> from typing import Optional
>>> from collections.abc import Callable
>>> Optional[Callable[[bytes], bytes]]
typing.Optional[collections.abc.Callable[[bytes], bytes]]

[ofek]

Ah I see, thanks!

[herambnemlekar]

Callable

Which deprecated version did you use for typing.Callable? I am facing the same issue with Python 3.9