why __getitem__ cannot be classmethod?

Question

Suppose following class:

class Class(object):
    @classmethod
    def getitem(*args):
        print \'getitem %s\' % (args,)
    @classmethod
    def __geti         


        

Answer 1

When you call x[test], the interpreter inspects type(x) for the __getitem__ attribute. In case of Class[test] it's the Class's metaclass, i.e. type. If you want to have a class-wide __getitem__, define it inside a new metaclass. (Needless to say, that's a sort of magic, as anything you do with metaclasses)

class Meta(type):
    def __getitem__(self, arg):
        print "__getitem__:", arg


class X(object):
    __metaclass__ = Meta

X['hello'] # output: __getitem__ hello