Practice Arena

Python Coding
Challenges

Write real Python in the browser. Instant feedback. From beginner to expert.

819 challenges 506 easy 280 medium 33 hard

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All Python Basics Strings & Text Lists & Arrays Dicts & Sets Functions & Closures OOP & Classes Data Structures & Algorithms Advanced Python Iterators & Generators Decorators & Context Managers Error Handling & Exceptions Regular Expressions Math & Number Theory Bit Manipulation Dynamic Programming Trees & Binary Trees Graphs & Graph Algorithms Recursion & Backtracking Greedy Algorithms Binary Search Two Pointers & Sliding Window Stacks & Queues Heaps & Priority Queues Linked Lists Matrix & 2D Arrays Datetime & Time Calculations Data Formats & Parsing SQL & SQLite Numpy & Vectorized Computing Cryptography & Hashing

Graphs & Graph Algorithms easy

Cycle Detection in a Directed Graph

Use DFS with a recursion stack to detect cycles in a directed graph.

graph dfs cycle

Graphs & Graph Algorithms easy

Cycle Detection in Undirected Graph

Write a function that detects if an undirected graph contains a cycle.

graph dfs cycle-detection

Graphs & Graph Algorithms easy

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.

graphs cliques adjacency-matrix

Showing 3 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.