How are Python metaclasses different from regular class inheritance? [duplicate]

Question

This might be too much of an open ended question, but I'm just now learning about metaclasses in Python and I don't understand how a metaclass is any different than just having a child class inherit from the parent class, like

class child(parent): 

Wouldn't this serve the same purpose of a metaclass? I guess maybe I don't understand the purpose of a metaclass.

Answer 1

The difference is that inheriting from a class does not affect how the class is created, it only affects how instances of the class are created. If you do:

class A(object):     # stuff  class B(A):     # stuff 

then A does not have any opportunity to "hook in" when B is created. Methods of A may be called when an instance of B is created, but not when the class B itself is created.

Metaclasses allow you to define custom behavior for when a class is created. Refer to the question I marked as duplicate for examples of how metaclasses work, and convince yourself that there are effects in those examples that you can't achieve with normal inheritance.