A class method which behaves differently when called as an instance method?

Question

I\'m wondering if it\'s possible to make a method which behaves differently when called as a class method than when called as an instance method.

For example, as a skill

Answer 1

You can reassign your identity method in init with short lambda function:

class Matrix(object):
    def __init__(self):
        self.identity = lambda s=self:s.__class__.identity(s)

        #...whatever initialization code you have...
        self.size = 10        

    @classmethod
    def identity(self, other):
        #...always do you matrix calculations on 'other', not 'self'...
        return other.size


m = Matrix()
print m.identity()
print Matrix.identity(m)

If you're not familiar with lambda, it creates an anonymous function. It's rarely necessary, but it can make your code more concise. The lambda line above could be rewritten:

    def identity(self):
        self.__class__.indentity(self)
    self.identity = identity