Ulrich Eckhardt wrote: > Hello! > > I just stumbled over a case where Python (2.7 and 3.3 on MS Windows) > fail to detect that an object is a function, using the callable() > builtin function. Investigating, I found out that the object was indeed > not callable, but in a way that was very unexpected to me: > > class X: > @staticmethod > def example(): > pass > test1 = example > test2 = [example,] > > X.example() # OK > X.test1() # OK > X.test2[0]() # TypeError: 'staticmethod' object is not callable
Slightly modified example: >>> @staticmethod ... def example(): return 42 ... >>> class X: ... example = example ... >>> X.example() 42 >>> example() Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: 'staticmethod' object is not callable When you access an attribute its __get__() method is implicitly called. This is part of the descriptor protocol: >>> X.example <function example at 0x7fe45c0ea3b0> >>> example <staticmethod object at 0x7fe45aafc090> >>> example.__get__(X) <function example at 0x7fe45c0ea3b0> While it would be easy to make staticmethod callable >>> class Staticmethod(staticmethod): ... def __call__(self, *args, **kw): ... return self.__func__(*args, **kw) ... >>> @Staticmethod ... def foo(): return "bar" ... >>> foo() 'bar' >>> X.baz = foo >>> X.baz() 'bar' I see no clear advantage over the current situation. > Bug or feature? No bug. Missing feature if you come up with a convincing use-case. -- http://mail.python.org/mailman/listinfo/python-list
