Practice Arena

Python Coding
Challenges

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

925 challenges 556 easy 323 medium 46 hard

All Easy Medium Hard

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

Strings & Text medium

Run-length encoding

Compress consecutive identical characters, e.g. 'aaabbc' → 'a3b2c1'.

strings compression

Strings & Text easy

Expand compressed string

Implement a function that expands run-length encoded strings (e.g., 'a3b2' → 'aaabb').

strings parsing run-length-encoding

Strings & Text easy

Hex encode decode

Write hex_encode and hex_decode to convert between hex strings and integer byte values.

hex encoding strings

Lists & Arrays easy

One Hot Encode Labels

Given a list of categorical labels, return a list of one-hot encoded vectors based on the sort order of unique labels.

lists encoding matrices

Bit Manipulation easy

Gray Code Encode

Implement a function that converts a non-negative integer to its Gray code representation using bitwise XOR and shift.

bitwise gray-code encoding

Stacks & Queues medium

Decode Nested String

Implement a function that decodes a string with nested encoding patterns.

stack string parsing

Data Formats & Parsing medium

Base64 Encode/Decode

Implement two functions to encode and decode Base64 strings using the standard alphabet and padding.

base64 encoding string

Data Formats & Parsing easy

Encode Base64 String

Write a function that encodes a UTF-8 string into a base64 string without using the base64 module.

base64 encoding strings

Data Formats & Parsing medium

Base64 Encode Decode

Implement Base64 encoding and decoding functions that handle padding and all standard characters.

base64 encoding decoding

Showing 1–9 of 9 challenges

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.