Normalize quotes
Replace all typographic quote characters with straight ASCII quotes.
Anagram Groups by Size
Group a list of words into anagram groups and return them sorted by group size and lexicographically.
Employee Hierarchy
Build an employee hierarchy tree and compute the total number of direct and indirect reports for each employee.
Employees earning more than manager
Given employee records with manager IDs, find those who earn more than their direct manager.
Graph DFS Generator
Implement a generator function that performs a depth-first traversal of a graph without recursion.
Cycle Detection in a Directed Graph
Use DFS with a recursion stack to detect cycles in a directed graph.
Cycle Detection in Undirected Graph
Write a function that detects if an undirected graph contains a cycle.
Find the Town Judge
Given n people and a trust array, return the town judge or -1.
Find center of star graph
Write a function that finds the center node of a star graph from its list of edges in O(1) time.
Keys and Rooms
A classic graph traversal challenge: check if all rooms are reachable from room 0 using keys found in visited rooms.
Clique Detection
Given an undirected graph and a list of vertices, check if every pair of distinct vertices in the list is connected by an edge.
Constant Time Compare
Write a function that compares two strings without leaking length or content via timing.
Verify HMAC signature
Implement a function that verifies an HMAC-SHA256 signature for a message and key.
Showing 1–13 of 13 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.