GeezerVison is showing github.com — `functools.partialmethod` simplification · Issue #124652 · python/cpython
functools.partialmethod simplification #124652
Open 3 / 33 of 3 issues completedOpen 3 / 33 of 3 issues completed DescriptionFeature or enhancement
Proposal:
Now, as partial has __get__ and Placeholder it is probably a good idea to simplify partialmethod.
So the mental model of partialmethod can simply be:
partial, which always has the first argument set to Placeholder.
So partialmethod could maybe be a subclass partial, which would potentially simplify things.
Also, maybe there is a way so that partialmethod can be made obsolete altogether.
Will see where I can get to with this.
Any ideas welcome.
Has this already been discussed elsewhere?
This is a minor feature, which does not need previous discussion elsewhere
Links to previous discussion of this feature:
#121027
#119827 (comment)
Linked PRs
Activityrhettinger commented on Sep 27, 2024 Note that partialmethod also copies __isabstractmethod__ from the underlying callable. Reacted by Nice Zombies and dgpb dg-pb commented on Oct 2, 2024 ContributorAuthor More actions PR is ready for review.
Quick summary of what I have done and thought of:
- Considered implementing
__isabstractmethod__ property for partial so that it returns it from the wrapped function. However, this is not a good idea, because in this case it would be impossible to set __isabstractmethod__ property for it. Also, it would be a divergent behaviour from FunctionType. In short, I kept the same abstract method attribute logic for partial and partialmethod as before.
- Relaxed trailing placeholder restriction. This way the behaviour of object is more robust, more functional and behaves naturally given functionality definition. E.g. If I know that
Placeholder is for positional arguments, then trailing placeholder will convert it to "positional only". And I can not see a good reason why trailing placeholders need to be prohibited. Also, such behaviour stems naturally from definition of functionality, while forbidding or automatically trimming trailing placeholders would require special mention in documentation.
partialmethod could be made redundant for standard method cases. However, there is one case that it is able to handle that could not be done without it, which is "Unknown descriptor" case, where partial needs to be applied at runtime on callable which is returned from __get__ of wrapped function.
E.g.:
class D:
def __get__(self, obj, cls):
return (lambda a, b: None)
class A:
d = D()
@staticmethod
def s(a, b):
pass
@classmethod
def c(self, a, b):
pass
ps = staticmethod(partial(s.__wrapped__, 1))
pc = classmethod(partial(c.__wrapped__, Placeholder, 1))
pd = ? # needs `partialmethod`Thus, I have modified partialmethod so that it does not do any heavy partial-like logic itself, but instead passes all of it to partial.
This allowed removing partialmethod special casing from inspect.signature.
More details in description of PR. dg-pb commented on Jan 6, 2025 ContributorAuthor More actions Likely most convenient merge order
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