bpo-34995: Maintain func.isabstractmethod in functools.cached_property by mwilbz · Pull Request #9904 · python/cpython (original) (raw)
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| @@ -882,6 +882,7 @@ def __init__(self, func): |
|---|
| self.func = func |
| self.attrname = None |
| self.__doc__ = func.__doc__ |
| self.__isabstractmethod__ = getattr(func, '__isabstractmethod__', False) |
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Would it be possible to only set the attribute (on self) if the attribute exists on func?
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Sure! Updated the implementation
| def calculate(self): |
|---|
| pass |
| with self.assertRaises(TypeError): |
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Would it be possible to (also) directly check the isabstractmethod attribute?
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Good suggestion, added an assertion for that
| @@ -882,6 +882,9 @@ def __init__(self, func): |
|---|
| self.func = func |
| self.attrname = None |
| self.__doc__ = func.__doc__ |
| func_isabstractmethod = getattr(func, '__isabstractmethod__') |
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Used like that, getattr() raises an exception if the attribute doesn't exist.
You can use:
try: self.__isabstractmethod__ = func.__isabstractmethod__
except AttributeError: pass
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Ah, thank you. I opened the implementation in my IDE and it said default=None so I was mislead. Pushing the version you're suggesting
| def calculate(self): |
|---|
| pass |
| self.assertTrue(getattr(AbstractExpensiveCalculator.calculate, '__isabstractmethod__', False)) |
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self.assertTrue(AbstractExpensiveCalculator.calculate.isabstractmethod) is enough.
| self.assertTrue(getattr(AbstractExpensiveCalculator.calculate, '__isabstractmethod__', False)) |
|---|
| with self.assertRaises(TypeError): |
| AbstractExpensiveCalculator() |
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Can you add a test on a method which doesn't have the __isabstractmethod__ attribute? I expect such test:
self.assertFalse(hasattr(AbstractExpensiveCalculator.calculate, '__isabstractmethod__'))
| @@ -0,0 +1 @@ |
|---|
| Maintain wrapped method's __isabstractmethod__ in functools.cached_property |
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I suggest:
:func:`functools.cached_property` now also copies the wrapped method's ``__isabstractmethod__`` attribute.
A Python core developer has requested some changes be made to your pull request before we can consider merging it. If you could please address their requests along with any other requests in other reviews from core developers that would be appreciated.
Once you have made the requested changes, please leave a comment on this pull request containing the phrase I have made the requested changes; please review again. I will then notify any core developers who have left a review that you're ready for them to take another look at this pull request.
I have made the requested changes; please review again
Thank you for your comments @vstinner ! Good suggestions around better test coverage + documentation. :)
Thanks for making the requested changes!
@vstinner: please review the changes made to this pull request.
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I still think that it is better to use @property instead of @cached_property in abstract classes, but I have no strong objections. What would say ABC experts?
| def calculate(self): |
|---|
| pass |
| self.assertTrue(AbstractExpensiveCalculator.calculate.__isabstractmethod__) |
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Too long line. Maybe make the class or property name a little shorter?
Possibly outside the scope of this change, but I noticed that update_wrapper in functools is a common way to inherit various standard fields in a wrapped method. For example, it's used here: https://github.com/python/cpython/blob/master/Lib/functools.py#L906 This example also happens to maintain __isabstractmethod__ in its own way, slightly different from this PR's current implementation.
Is it worth considering more generally modifying the standard fields to update via update_wrapper to include __isabstractmethod__ as well? https://github.com/python/cpython/blob/master/Lib/functools.py#L30 Then cached_property can simply reuse update_wrapper to be consistent with other wrappers in functools.
Regardless of my previous comment, what are the next steps to move forward with this PR? Anything I can do? Thanks again for the reviews up until now =)
It sounds like there isn't interest from core contributors in merging this change, so I'll close the PR. Thanks reviewers for your time and feedback!