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Python Coding
Challenges

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467 challenges 330 easy 120 medium 17 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

Python Basics easy

Find Missing Number

Given a list of n distinct integers from 0..n with one missing, return the missing number.

math integers arrays

Lists & Arrays easy

Second Largest Unique Value

Return the second largest distinct integer from a list, or None if it doesn't exist.

sorting unique arrays

Lists & Arrays easy

Find Missing Number 1 to n

Given a list containing n-1 distinct integers from 1 to n, find the missing number without using extra space.

arrays math search

Lists & Arrays easy

Union of Two Lists

Implement a function that combines two lists and returns only unique elements.

Dicts & Sets easy

Set intersection size

Count how many distinct values appear in both of two given lists.

sets intersection counting

Dicts & Sets easy

Count Pairs with Sum

Implement a function that counts the number of distinct pairs in a list summing to a target.

dictionary pair-counting hash-map

Bit Manipulation easy

Missing Number XOR

Given a list of n distinct numbers from 0 to n with one missing, use XOR to find and return the missing number.

xor bitwise arrays

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

Dynamic Programming medium

Coin Change Ways

Count the number of distinct combinations of coins that sum to a target amount.

dynamic programming coins counting

Recursion & Backtracking easy

Permutation Generator

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

recursion backtracking permutations

Recursion & Backtracking medium

Combination Generator

Write a recursive function that returns all combinations of length k from a list of distinct integers.

recursion backtracking combinations

Two Pointers & Sliding Window hard

Subarrays with K different ints

Count the number of contiguous subarrays that contain exactly K distinct integers.

sliding-window two-pointers hashmap

Showing 12 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.