Rotate Left by k
Implement a function that rotates a list left by k positions.
Find Missing Number 1 to n
Given a list containing n-1 distinct integers from 1 to n, find the missing number without using extra space.
Interleave Two Lists
Write a function that interleaves two lists element by element, preserving order.
Keep only even indexes
Given a list, return a new list containing only the elements at even indices (0, 2, 4, ...).
Running Maximum
Implement a function that returns a list where each element is the largest value seen so far.
Difference of Consecutive Elements
Given a list of numbers, return a new list where each element is the difference between consecutive elements.
All Unique Values Keep Order
Remove duplicates from a list, keeping only the first occurrence of each value while preserving relative order.
Insert into a Sorted List
Implement a function that inserts a value into a sorted list at the correct position using binary search.
Average excluding min and max
Return the average of a list after discarding the lowest and highest elements, handling edge cases.
Zip lists into pairs
Write a function that takes two lists and returns a list of two-element sublists pairing elements by index up to the shortest length.
Longest Run of Equal Values
Compute the length of the longest run (consecutive block) of equal elements in a list.
Middle Element of an Odd-Length List
Implement a function that returns the middle element of an odd-length list.
Is Subset of Another List
Write a function that returns True if every element in a given list exists in another list, ignoring duplicates.
Unzip pairs into two lists
Write a function that takes a list of pairs and returns two separate lists: first elements and second elements.
Generate a Multiplication Table
Build a function that returns an n x n multiplication table as a list of lists.
Find Second Largest
Find the second largest unique number in a list, or None if it doesn't exist.
Move Zeros to End
Rearrange a list by moving all zeros to the end while preserving the relative order of non-zero elements.
Majority Element Finder
Implement a function that returns the majority element in a list, which appears more than half the time.
Intersection of Two Lists
Given two lists, return a sorted list of unique elements that appear in both lists.
Union of Two Lists
Implement a function that combines two lists and returns only unique elements.
Difference of Two Lists
Write a function that returns items in list a that are not in list b, preserving order and duplicates.
Chunk list into groups
Implement a function that splits a list into sublists of a given size.
Zip Two Lists
Write a function that pairs elements from two lists by index, stopping at the shorter list.
Rearrange Positives and Negatives
Write a function that rearranges a list in-place so all negative numbers come before non-negative numbers.
Showing 49–72 of 186 challenges · easy
Guide: free Python coding challenges
Practice Python by solving problems
PythonSkillset challenges are hands-on coding exercises from beginner to advanced. Open a challenge, read the problem, write Python in the split-pane editor, and run tests with Pyodide — no install required.
How to use the arena
- Pick a category — basics, algorithms, strings, and more
- Open a challenge, read the statement, and edit the starter code
- Run tests, fix failures, then try a related quiz or tutorial lesson
Challenges vs tutorials and quizzes
Challenges test what you can build under constraints. For guided teaching, use our Python tutorials. For quick checks, try quizzes or copy snippets from code samples.