How do you make a higher order function in Python

Question

How to make a higher-order function in Python? Can it be done by using callable objects?

Answer 1

You have two choices to create higher-order functions: you can use nested scopes or you can use callable objects. For example, suppose you wanted to define line(a,b) which returns a function f(x) that computes the value a*x+b. 

Using nested scopes:

def line(a, b):
    def result(x):
        return a * x + b
    return result

Or using a callable object:

class line:

    def __init__(self, a, b):
        self.a, self.b = a, b

    def __call__(self, x):
        return self.a * x + self.b

In both cases,

taxes = line(0.3, 2)