Is there a way to implement methods like __len__ or __eq__ as classmethods?

Question

It is pretty easy to implement __len__(self) method in Python so that it handles len(inst) calls like this one:

class A(object):

          


        

Answer 1

Since a class is an instance of a metaclass, one way is to use a custom metaclass:

>>> Meta = type('Meta', (type,), {'__repr__': lambda cls: 'class A'})
>>> A = Meta('A', (object,), {'__repr__': lambda self: 'instance of class A'})
>>> A
class A
>>> A()
instance of class A