metaclass

>>> class mytype(type):
...     def __new__(meta, clsname, bases, methods):
...             print('Creating: ', clsname)
...             return super().__new__(meta, clsname, bases, methods)
... 
>>> class Spam(metaclass=mytype):
...     def __init__(self, y):
...             self.y = y
...     def bar(self):
...             print('bar')
... 
Creating:  Spam
>>>