Passing Functions as Arguments¶

Let us understand how to pass functions as arguments using Python as programming language.

The function which takes other functions as arguments is typically called as higher order function and the function which is passed as argument is called as lower order function.
You need to define all the functions you want to pass as argument for the higher order functions.
For simple functionality, we can also pass unnamed functions or lambda functions on the fly. We will see as part of the next topic.
Let us take the example of getting sum of integers, squares, cubes and evens related to passing functions as arguments.

Regular Functions

list(range(1, 10))

[1, 2, 3, 4, 5, 6, 7, 8, 9]

list(range(1, 10, 2))

[1, 3, 5, 7, 9]

list(range(1, 10, 3))

[1, 4, 7]

def sum_of_integers(lb, ub):
    total = 0
    for i in range(lb, ub + 1):
        total += i
    return total

sum_of_integers(5, 10)

def sum_of_squares(lb, ub):
    total = 0
    for i in range(lb, ub + 1):
        total += i * i
    return total

sum_of_squares(5, 10)

def sum_of_cubes(lb, ub):
    total = 0
    for i in range(lb, ub + 1):
        total += i * i * i
    return total

sum_of_cubes(5, 10)

def sum_of_evens(lb, ub):
    total = 0
    for i in range(lb, ub + 1):
        total += i if i % 2 == 0 else 0
    return total

sum_of_evens(5, 10)

Using Functions as arguments

def my_sum(lb, ub, f):
    total = 0
    for e in range(lb, ub + 1):
        total += f(e)
    return total

def i(n): return n

def sqr(n): return n * n

def cube(n): return n * n * n

def even(n): return n if n % 2 == 0 else 0

my_sum(5, 10, i)

my_sum(5, 10, sqr)

my_sum(5, 10, cube)

my_sum(5, 10, even)

Mastering Python