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

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

Python Basics easy

Insert New Row

Implement a function that inserts a new row into a 2D list at a specified index.

lists insert rows

Python Basics easy

Fancy Index Select

Given a 2D matrix and a list of row indices, select those rows in order and return them as a new 2D list.

indexing lists matrix

Strings & Text medium

Zigzag string conversion

Encode a string in zigzag order across numRows rows, then read row by row.

Greedy Algorithms medium

Minimum Number of Arrows to Burst Balloons

Given balloon intervals, find the minimum number of arrows to burst all balloons by merging overlaps.

greedy sorting intervals

Binary Search medium

Search 2D Matrix

Given a sorted 2D matrix with sorted rows and first element of each row greater than last of previous, find target efficiently.

binary search 2d matrix searching

Matrix & 2D Arrays easy

Valid Sudoku Board

Determine if a 9x9 Sudoku board is valid by checking rows, columns, and 3x3 sub-boxes.

matrix set validation

Matrix & 2D Arrays easy

Valid Sudoku Validator

Determine if a given 9x9 Sudoku board is valid by checking rows, columns, and 3x3 boxes.

matrix validation set

Data Formats & Parsing easy

Update Row by ID

Given a list of CSV rows and target ID, replace the first matching row's value.

csv parsing list

SQL & SQLite easy

Inner Join Two Tables

Write a function that inner joins two lists of dictionaries on a common key and returns the combined rows.

sql join dictionaries

SQL & SQLite medium

Index Creation Query

Create an in-memory SQLite database, execute CREATE INDEX statements, and return the resulting index metadata rows.

sqlite create-index schema

Showing 10 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.