At what point do methods in Python acquire a get property? —As soon as they're defined in the class? Why does Python let me define a method without any arguments (not even a first self argument)?
I know how to use classmethod and staticmethod, and I know that they're built-in functions, but what happens to a function that is so-decorated?
Essentially, I'm wondering about the "magic" that happens between class definition and class construction.
Check this out.
https://docs.python.org/3/howto/descriptor.html#class-methods
You can also take a look at the source code for class and static method objects, in funcobject.c:
http://hg.python.org/cpython/file/69b416cd1727/Objects/funcobject.c
Class method object definition starts on line 694, while static method object definition starts on line 852. (I do find it kind of funny that they have items titled "method" in funcobject.c when methodobject.c also exists.)
class ClassMethod: implementation of "Emulate PyClassMethod_Type() in Objects/funcobject.c" found at docs.python.org/3/howto/descriptor.html#class-methods
types.FunctionType.__get__ is defined to implement instance methods. classmethod and staticmethod just provide suitable definitions of __get__ to implement class- and static-method behavior, respectively. (For example, staticmethod.__get__ always returns the underlying function instead of a method object.)For reference, from the first link in @JAB's answer
Using the non-data descriptor protocol, a pure Python version of staticmethod() would look like this:
class StaticMethod(object): "Emulate PyStaticMethod_Type() in Objects/funcobject.c" def __init__(self, f): self.f = f def __get__(self, obj, objtype=None): return self.f
...
Using the non-data descriptor protocol, a pure Python version of classmethod() would look like this:
class ClassMethod(object): "Emulate PyClassMethod_Type() in Objects/funcobject.c" def __init__(self, f): self.f = f def __get__(self, obj, klass=None): if klass is None: klass = type(obj) def newfunc(*args): return self.f(klass, *args) return newfunc
