Higher-Order Function

what is a Higher-Order Function?

In Python a higher-order function is a function that takes takes one or more function as arguments, return a function as its result or both.

In other words, it treats functions as first-class citizens, allowing them to be manipulated just like any other object such as integers, string or list.

most common Higher-Order Function

• map()

• filter()

• reduce()

map() - Applying a Function to Each Element in an iterable

The map() function takes a function and an iterable (e.g, a list) as input and applies the function to each element in the iterable, returning a new iterable with the result.

def square(x):
    return x * x
number = [1,2,3,4,5,6]
squared_number = map(square, number)
print(list(squared_number))    # Output: [1,4,9,16,25,36]

filter() - Filtering Elements in an Iterable

The filter() function takes a function and an iterable as input and return a new iterable containing only the elements for which the function return True.

def even(x):
    return x % 2 == 0
number = [1,2,3,4,5,6]
even_number = filter(even, number)
print(list(even_number)) # Output: [2,4,6]

reduce() - Aggregating Elements in an Iterable

The reduce() function takes a function and an iterable as input and successively applies the function to the elements, reducing the iterable to a single value.

from functools import reduce

def add(x, y):
    return x + y

numbers = [1,2,3,4,5]
sum_of_number = reduce(add, numbers)

print(sum_of_number) # Output: 15