Repository navigation
Descriptors shouldn't be considered callable inside class definition #2267
Description
The following is an error in Python but passes mypy's checks:
class X:
@staticmethod
def f(): pass
f()Error:
Traceback (most recent call last):
File "cls.py", line 1, in <module>
class X:
File "cls.py", line 4, in X
f()
TypeError: 'staticmethod' object is not callable
Same thing goes for classmethod.
Activity
gvanrossum commentedon Oct 17, 2016
Ugh. Mypy's lack of understanding of class vs. instance attributes strikes again. :-(
elazarg commentedon Oct 17, 2016
I would expect mypy to mimic the runtime - treat the current block as if it was not inside a class definition, then send the definitions to a "metaclass" (hard coded, in the case to
type) to handle. It will also yield a natural extension point for a plugin: implement your home-made "metaclass".Does that make sense at all? As far as I understand, this isn't how it's done, currently - not even remotely similar.
gvanrossum commentedon Oct 20, 2016
Would be good to fix but probably complicated.
gvanrossum commentedon Jan 7, 2017
I think you meant "decorators" in the title, not "descriptors", right? (A decorator uses
@syntax -- a descriptor is something that implements__get__and (optionally)__set__and__delete__.refi64 commentedon Mar 27, 2017
@gvanrossum Well, I meant descriptors because of the
staticmethoddescriptor.gvanrossum commentedon Mar 27, 2017
Ah, got it.
erictraut commentedon Apr 8, 2022
This doesn't appear to generate a runtime exception with newer versions of Python, so it's no longer a false negative in mypy.
JelleZijlstra commentedon Apr 8, 2022
The runtime change is from https://bugs.python.org/issue43682 which was included in Python 3.10.
hauntsaninja commentedon Aug 27, 2023
Closing as won't fix, though if anyone feels inspired to write a PR for 3.9 feel free to