Expert Python Programming - Third Edition

Class decorators

One of the lesser known syntax features of Python are the class decorators. Their syntax and implementation is exactly the same as function decorators, as we mentioned in Chapter 3, Modern Syntax Elements – Below the Class Level. The only difference is that they are expected to return a class instead of the function object. Here is an example class decorator that modifies the __repr__() method to return the printable object representation, which is shortened to some arbitrary number of characters:

def short_repr(cls): 
    cls.__repr__ = lambda self: super(cls, self).__repr__()[:8] 
    return cls 
 
@short_repr 
class ClassWithRelativelyLongName: 
    pass 

The following is what you will see in the output:

>>> ClassWithRelativelyLongName() ...