Expert Python Programming - Third Edition

Decorators – a method of metaprogramming

The decorator syntax was explained in Chapter 3, Modern Syntax Elements – Below the Class Level, as a syntactic sugar for the following simple pattern:

def decorated_function(): 
    pass 
decorated_function = some_decorator(decorated_function)

This verbose form of function decoration clearly shows what the decorator does. It takes a function object and modifies it at runtime. As a result, a new function (or anything else) is created based on the previous function object with the same name. This decoration may be a complex operation that performs some code introspection or decorated function to give different results depending on how the original function was implemented. All this means ...