List comprehension in Python

List comprehension is the method to create a new list from the value of an existing list. Generally, list comprehension is more compact and faster than normal functions and loops for creating lists. List comprehension always comes with a for-loop wrapped inside the square bracket.

Syntax of list_comprehension:

new_list = [expression for item in iterable]

We can use this syntax with an example so that we have a clear idea about how to use list comprehension.

Example:

a_list = [1,2,3,4,5]

if we need to get the square of the items in a list then,

	new_list = [item**2 for item in a_list]

We have easily created a new_list with output [1, 4, 9, 16, 25], the square of values of a_list. If list comprehension is not available in python then we have to write multiple lines of code which is written below.

new_list = []
a_list = [1,2,3,4,5]
for item in a_list:
	new_list.append(item**2)

List comprehension with if condition

Syntax:

new_list = [expression for item in iterable if condition == True]

Example:

		new_list  = [item for item in a_list if item%2 ==0]

This code will create a list of even numbers only from values of a_list, output as [2, 4]. We can use if condition with for loop in a single line.