How to Use List Comprehension with Condition in Python

Use list comprehension with an if condition placed after the expression to filter items. The syntax is [expression for item in iterable if condition], which creates a new list including only items that meet the condition.

Syntax

The basic syntax for list comprehension with a condition is:

• expression: The value or operation to include in the new list.
• item: A variable representing each element from the iterable.
• iterable: The collection you loop over (like a list or range).
• if condition: A filter that only includes items where the condition is True.

python

[expression for item in iterable if condition]

Example

This example creates a list of even numbers from 0 to 9 using list comprehension with a condition.

python

even_numbers = [x for x in range(10) if x % 2 == 0]
print(even_numbers)

Output

[0, 2, 4, 6, 8]

Common Pitfalls

Common mistakes include placing the if condition before the for loop or forgetting to include the condition altogether.

Wrong order example (causes syntax error):

python

numbers = [x for if x % 2 == 0 in range(10)]  # Incorrect syntax

# Correct way:
numbers = [x for x in range(10) if x % 2 == 0]

Quick Reference

Remember these tips for using list comprehension with conditions:

• Put the if condition after the for loop.
• The condition filters which items to include.
• You can use any valid expression before the for.
• List comprehensions are concise and readable alternatives to loops with append().

Key Takeaways

Place the if condition after the for loop in list comprehension to filter items.

List comprehension with condition creates a new list including only elements that meet the condition.

Avoid syntax errors by not placing if before for in the comprehension.

Use list comprehension for concise and readable filtering instead of loops with manual appending.