Introduction to Python (by Ilan Schnell)

Higher order functions

A higher-order function takes functions as input and returns new functions.

def compliment(f):
    """
    Returns the compliment (which is a function) of function f.
    """
    def res(*args):
        return not f(*args)
    return res

def even(n):
    return bool(n % 2 == 0)

odd = compliment(even)

Note that the argument of compliment is not limited to a function which only takes one argument.

Without the higher-order function compliment, we would have to write:

def odd(n):
    return not even(n)