Python Comprehensions: List, Dictionary, and Set with Examples

 

Python Comprehensions

1. List Comprehension

Definition:
List comprehension is a concise way to create lists by applying an expression to each item in an existing iterable.

Syntax:

[expression for item in iterable if condition]

Example:

# List comprehension to create a list of squares
squares = [x**2 for x in range(5)]  # Square each number from 0 to 4

print(squares)  # Output: [0, 1, 4, 9, 16]

2. Dictionary Comprehension

Definition:
Dictionary comprehension allows creating a dictionary from an iterable using a key-value pair.

Syntax:

{key_expression: value_expression for item in iterable if condition}

Example:

# Dictionary comprehension to create a dictionary with numbers and their squares
squares_dict = {x: x**2 for x in range(5)}

print(squares_dict)  # Output: {0: 0, 1: 1, 2: 4, 3: 9, 4: 16}

3. Set Comprehension

Definition:
Set comprehension is similar to list comprehension but creates a set. Sets automatically remove duplicate values.

Syntax:

{expression for item in iterable if condition}

Example:

# Set comprehension to create a set of squares
squares_set = {x**2 for x in range(5)}

print(squares_set)  # Output: {0, 1, 4, 9, 16}