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

Dynamic Programming easy

Climbing Stairs

Implement a function that returns the number of distinct ways to climb n stairs using steps of 1 or 2.

fibonacci dp counting

Trees & Binary Trees easy

Binary Tree Inorder Traversal

Implement an inorder traversal function that returns node values in left-root-right order.

binary-tree traversal recursion

Trees & Binary Trees easy

Preorder Traversal

Implement a function that returns the preorder traversal values of a binary tree.

binary-tree traversal recursion

Trees & Binary Trees easy

Postorder Traversal

Implement a function that returns the postorder traversal of a binary tree as a list of node values.

binary-tree traversal recursion

Recursion & Backtracking easy

Permutation Generator

Write a function that returns all permutations of a list of distinct integers.

recursion backtracking permutations

Recursion & Backtracking easy

Permutations

Write a function that returns every permutation of the elements in the input list.

recursion backtracking permutations

Binary Search easy

Upper Bound Binary Search

Write a function that returns the index of the first element greater than a target in a sorted list.

binary-search arrays searching

Two Pointers & Sliding Window easy

Longest Substring Without Repeating Characters

Implement a function that returns the length of the longest substring without repeating characters.

strings sliding-window two-pointers

Two Pointers & Sliding Window easy

Squares of Sorted Array

Implement a function that returns a sorted list of squares for a given non-decreasing integer array.

two-pointers sorting array

Matrix & 2D Arrays easy

Diagonal Traverse Matrix

Implement a function that returns all elements of a matrix in diagonal zigzag order.

matrix traversal array

Matrix & 2D Arrays easy

Transpose Matrix In-Place

Implement a function that transposes a square matrix in-place and returns the transposed matrix.

matrix transpose in-place

Matrix & 2D Arrays easy

Matrix Multiply 2D

Write a function that multiplies two 2D matrices (lists of lists) and returns the product matrix.

matrix multiplication nested-loops

Matrix & 2D Arrays easy

Transpose 2D Array

Implement a function that returns the transpose of a rectangular 2D list.

matrix transpose nested-lists

Datetime & Time Calculations easy

Days in month

Write a function that returns the number of days in a given month and year, correctly handling leap years.

datetime calendar leap-year

Datetime & Time Calculations easy

Days Between Dates

Write a function that returns the number of days between two given dates.

datetime date-arithmetic calendar

Datetime & Time Calculations easy

Weekday from date

Write a function that returns the full English weekday name for a date string.

datetime date weekday

Datetime & Time Calculations easy

Leap Years in Range

Write a function that returns a list of all leap years between two given years, inclusive.

leap-year range datetime

Datetime & Time Calculations easy

Unix timestamp to datetime

Write a function that returns a UTC datetime string from a Unix timestamp.

datetime unix-timestamp utc

Datetime & Time Calculations easy

Next Weekday Finder

Write a function that returns the next weekday date after a given date.

datetime date weekday

Datetime & Time Calculations easy

Schedule conflict check

Write a function that takes a list of time intervals and returns True if any two overlap.

datetime intervals overlap

Datetime & Time Calculations easy

Month End Date

Implement a function that returns the last day of the month for a given year and month.

datetime calendar leap-year

Data Formats & Parsing easy

Parse email header

Write a function that parses a raw email header string and returns sender, recipient, and subject.

parsing strings email

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 easy

Create Table Schema

Write a function that creates a SQLite table with a given name and columns, and returns the resulting schema as a list of column definitions.

sqlite schema table

Showing 97–120 of 127 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.