Decorator

• A function that changes the behaviour of other functions.
• The input of a decorator is a function.
• The returned value of a decorator is a modified version of the same function.

Normally a decorator is used with the @ prefix just above the declaration of a function:

from some_module import some_decorator

@some_decorator
def f(...):
    ...

However, that syntax is only to make it look nice. In reality it is basically the same as this code:

def f(...):
    ...

f = some_decorator(f)