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Issue using Protocol as a base class with Python 3.5.2 #734
Description
Python: 3.5.2
OS: macOS Mojave
Seems that _generic_new implementation from typing_extensions module is outdated or incorrect. When typing_extensions relies on its own implementation of _generic_new I get the following error.
Script to reproduce:
import abc
from typing_extensions import Protocol, runtime_checkable
@runtime_checkable
class Proto(Protocol):
@abc.abstractmethod
def foo(self):
pass
class SomeClass(Proto):
def __init__(self, some_arg):
pass
def foo(self):
return 5
x = SomeClass(3)
Traceback:
Traceback (most recent call last):
File "/Users/dikobraz/repro.py", line 20, in <module>
x = SomeClass(3)
File "/Users/dikobraz/env-py-3.5-tf-2/lib/python3.5/site-packages/typing_extensions.py", line 1357, in __new__
return _generic_new(cls.__next_in_mro__, cls, *args, **kwds)
File "/Users/dikobraz/env-py-3.5-tf-2/lib/python3.5/site-packages/typing_extensions.py", line 87, in _generic_new
return base_cls.__new__(cls, *args, **kwargs)
TypeError: object() takes no parameters
In debugger:
Activity
gvanrossum commentedon Jun 24, 2020
Could you try this with a newer version? 3.5 is nearing its end of life, and the latest version is 3.5.9. The latest version for which I can find downloadable binaries is 3.5.4: https://www.python.org/downloads/release/python-354/
If your problem is specifically with 3.5.2, I'm not sure that we can do much for you unless you can come up with a fix (I don't even have 3.5 installed on my machine any more).
Slonegg commentedon Jun 24, 2020
Thank you @gvanrossum for the quick reply. I've verified that it works with 3.5.9 because it comes with newer
typingmodule andtyping_extensionsmodule is just using_generic_newfromtyping.Maybe we can just use
_generic_newfrom more recent version oftypingmodule before it was removed completely in this PR (python/cpython#4906):However, since Python 3.5 nearing its end of life maybe it's not worth it. We just have 3.5.2 baked in our Docker images. What is your advise? Submit a PR for
typing_extensionsand see if it works or drop it? Worth noting though that Python 3.5.2 is default for Ubuntu 16.04 which is still widely used for deployment.gvanrossum commentedon Jun 24, 2020
I strongly advise you to upgrade your Python version.