List Comprehension in Python

List comprehension is a concise and elegant way to create new lists in Python. It allows you to transform, filter, and manipulate elements from an existing list to create a new list in a single line of code.

Syntax

The general syntax of list comprehension is:

new_list = [expression for item in iterable if condition]

• new_list: The new list that will be created.
• expression: The expression used to manipulate each element in the original list.
• item: The variable representing each element in the original list.
• iterable: The original list or any other iterable objects like strings, tuples, or sets.
• condition: (Optional) The condition that determines whether an element should be included in the new list.

Examples

Let's see some examples to get a better understanding of list comprehension.

1. Creating a new list by multiplying each element of an existing list by 2.

numbers = [1, 2, 3, 4, 5]
doubled = [num * 2 for num in numbers]
# doubled: [2, 4, 6, 8, 10]

2. Generating a list of even numbers from 1 to 10.

evens = [num for num in range(1, 11) if num % 2 == 0]
# evens: [2, 4, 6, 8, 10]

3. Filtering out vowels from a string.

sentence = "Hello, world!"
consonants = [char for char in sentence if char.lower() not in 'aeiou']
# consonants: ['H', 'l', 'l', ',', ' ', 'w', 'r', 'l', 'd', '!']

4. Creating a list of squares of numbers divisible by 3 from 0 to 9.

squares = [num ** 2 for num in range(10) if num % 3 == 0]
# squares: [0, 9, 36, 81]

List comprehension can be a powerful tool to simplify your code and make it more readable. It is a commonly used technique in Python programming, and mastering it can greatly enhance your productivity as a programmer.

For more information, refer to the Python documentation on list comprehension.