New submission from Jon McMahon <[email protected]>:
Subclasses of io.IOBase can be instantiated with abstractmethod()s, even though
ABCs are supposed to prevent this from happening. I'm guessing this has to do
with io using the _io C module because the alternative pure-python
implementation _pyio doesn't seem to have this issue. I'm using Python 3.6.7
>>> import _pyio
>>> import io
>>> import abc
>>> class TestPurePython(_pyio.IOBase):
... @abc.abstractmethod
... def foo(self):
... print('Pure python implementation')
...
>>> class TestCExtension(io.IOBase):
... @abc.abstractmethod
... def bar(self):
... print('C extension implementation')
...
>>> x=TestPurePython()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: Can't instantiate abstract class TestPurePython with abstract
methods foo
>>> y=TestCExtension()
>>> y.bar()
C extension implementation
>>>
----------
components: IO
messages: 335166
nosy: Jon McMahon
priority: normal
severity: normal
status: open
title: io.IOBase subclasses don't play nice with abc.abstractmethod
versions: Python 3.6
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Python tracker <[email protected]>
<https://bugs.python.org/issue35958>
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