How to Sort List of Tuples in Python: Simple Guide

To sort a list of tuples in Python, use the sorted() function or the list's .sort() method. You can sort by the first element by default or specify a different element using the key parameter with a lambda function.

Syntax

The basic syntax to sort a list of tuples is:

• sorted(list_of_tuples) - returns a new sorted list by the first tuple element.
• list_of_tuples.sort() - sorts the list in place by the first tuple element.
• sorted(list_of_tuples, key=lambda x: x[index]) - sorts by the tuple element at index.
• list_of_tuples.sort(key=lambda x: x[index]) - sorts in place by the tuple element at index.

python

sorted_list = sorted(list_of_tuples, key=lambda x: x[1])
list_of_tuples.sort(key=lambda x: x[1])

Example

This example shows how to sort a list of tuples by the second element in each tuple.

python

data = [(3, 'apple'), (1, 'banana'), (2, 'cherry')]
sorted_data = sorted(data, key=lambda x: x[1])
print(sorted_data)

Output

[(3, 'apple'), (1, 'banana'), (2, 'cherry')]

Common Pitfalls

Common mistakes include:

• Not using key when you want to sort by an element other than the first.
• Confusing sorted() (which returns a new list) with .sort() (which changes the list itself).
• Using an invalid index in the lambda function causing errors.

python

data = [(3, 'apple'), (1, 'banana'), (2, 'cherry')]
# Wrong: sorts by first element, not second
wrong_sorted = sorted(data)

# Right: sorts by second element
right_sorted = sorted(data, key=lambda x: x[1])

print('Wrong:', wrong_sorted)
print('Right:', right_sorted)

Output

Wrong: [(1, 'banana'), (2, 'cherry'), (3, 'apple')]
Right: [(3, 'apple'), (1, 'banana'), (2, 'cherry')]

Quick Reference

Summary tips for sorting lists of tuples:

• Use sorted() to get a new sorted list without changing the original.
• Use .sort() to sort the list in place.
• Use the key parameter with a lambda to sort by any tuple element.
• Remember tuple indexes start at 0.

Key Takeaways

Use sorted() or .sort() to sort lists of tuples in Python.

By default, sorting uses the first tuple element; use key=lambda x: x[index] to sort by other elements.

sorted() returns a new list; .sort() changes the original list.

Always check tuple indexes start at zero to avoid errors.

Sorting tuples is useful for organizing data by any tuple field.