Mastering Object-oriented Python

Parameterizing a decorator

Sometimes we want to provide more elaborate parameters to a decorator. The idea is that we are going to customize the wrapping function. When we do this, decoration becomes a two-step process.

When we write the following code, we provide a parameterized decorator to a function definition:

@decorator(arg)
def func( ):
    pass

The use of the decorator is a shorthand for the following code:

def func( ):
    pass
func= decorator(arg)(func)

Both examples do the following three things:

• Defined a function, func
• Applied the abstract decorator to its arguments to create a concrete decorator, decorator(arg)
• Applied the concrete decorator to the defined function to create the decorated version of the function, decorator(arg)(func)

This means that ...