Python - self, no self and cls

Question

Yet another question on what the \'self\' is for, what happens if you don\'t use \'self\' and what\'s \'cls\' for. I \"have done my homework\", I just want to make sure I go

Answer 1

You use self as the first argument in regular methods where the instance is passed automatically through this argument. So whatever the first argument is in a method - it points to the current instance

When a method is decorated with @classmethod it gets the class passed as its first argument so the most common name for it is cls as it points to the class.

You usually do not prefix any variables (hungarian notation is bad).

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Here's an example:

class Test(object):
    def hello(self):
        print 'instance %r says hello' % self
    @classmethod
    def greet(cls):
        print 'class %r greet you' % cls

Output:

>>> Test().hello()
instance <__main__.Test object at 0x1f19650> says hello

>>> Test.greet()
class  greet you