Eric V. Smith <[email protected]> added the comment:
Here's the error without dataclasses:
------
from typing import Protocol
class SomeProtocol(Protocol):
@property
def some_value(self) -> str: ...
class SomeClass(SomeProtocol):
def __init__(self, some_value):
self.some_value = some_value
if __name__ == '__main__':
a = SomeClass(some_value="value")
------
Traceback (most recent call last):
File "foo.py", line 12, in <module>
a = SomeClass(some_value="value")
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "foo.py", line 9, in __init__
self.some_value = some_value
^^^^^^^^^^^^^^^
AttributeError: property 'some_value' of 'SomeClass' object has no setter
And here it is without Protocol:
--------
class SomeProperty:
@property
def some_value(self) -> str: ...
class SomeClass(SomeProperty):
def __init__(self, some_value):
self.some_value = some_value
if __name__ == '__main__':
a = SomeClass(some_value="value")
--------
Traceback (most recent call last):
File "foo.py", line 10, in <module>
a = SomeClass(some_value="value")
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "foo.py", line 7, in __init__
self.some_value = some_value
^^^^^^^^^^^^^^^
AttributeError: property 'some_value' of 'SomeClass' object has no setter
----------
title: Inheritance from Protocol with property in dataclass makes them
non-instantiatable -> Inheritance from Protocol with property in class makes
them non-instantiatable
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Python tracker <[email protected]>
<https://bugs.python.org/issue47237>
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