Python List Examples

Overview

Short, copy-paste examples for the most common things you do with lists in Python. Run any of them in the online Python compiler.

Examples

Sum and average

nums = [10, 20, 30, 40]

total = sum(nums)          # 100
average = sum(nums) / len(nums)  # 25.0

Largest and smallest

nums = [3, 7, 2, 9, 4]
print(max(nums), min(nums))  # 9 2

Unique values (keeping order)

items = [1, 1, 2, 3, 3, 3]

unique = list(dict.fromkeys(items))  # [1, 2, 3] — order preserved
unique_unordered = list(set(items))  # also unique, but order not guaranteed

Filter and transform (comprehension)

nums = [1, 2, 3, 4, 5, 6]

doubled_evens = [n * 2 for n in nums if n % 2 == 0]
print(doubled_evens)  # [4, 8, 12]

Flatten a nested list

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

flat = [x for row in matrix for x in row]
print(flat)  # [1, 2, 3, 4, 5]

Any / all / find

nums = [1, 2, 3]

print(any(n > 2 for n in nums))   # True
print(all(n > 0 for n in nums))   # True
print(next((n for n in nums if n == 2), None))  # 2  (first match, else None)

Count occurrences

from collections import Counter

votes = ["a", "b", "a", "c", "b", "a"]
counts = Counter(votes)
print(counts["a"])          # 3
print(counts.most_common(1)) # [('a', 3)]

Join a list into a string

words = ["a", "b", "c"]
print(", ".join(words))  # a, b, c

Sort a copy (leave the original alone)

nums = [10, 1, 21, 2]
print(sorted(nums))  # [1, 2, 10, 21]  — see the how-to for key= and reverse=

Frequently asked questions

How do I sum a list of numbers in Python?

Use the built-in sum(my_list). For an average, divide by len(my_list).

How do I get unique values from a list?

list(dict.fromkeys(items)) keeps the original order; list(set(items)) is shorter but does not guarantee order.

How do I flatten a nested list?

Use a nested comprehension: [x for row in matrix for x in row].