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
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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
Bit Manipulation easy

Single Number XOR

Given a non-empty list of integers where every element appears twice except one, return the single number using XOR.

xor bit-manipulation arrays
+10 pts 12m
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
+10 pts 15m
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
+10 pts 15m
Bit Manipulation easy

Gray Code Decode

Implement gray_decode(n) that converts an n-bit Gray code integer back to its standard binary value using XOR accumulation.

gray-code bit-manipulation xor
+10 pts 15m
Bit Manipulation easy

Add without plus

Implement a function that adds two integers using only bitwise operations, no arithmetic plus or minus.

bitwise addition xor
+10 pts 15m
Bit Manipulation medium

Maximum XOR Pair

Implement max_xor_pair(nums) that returns the maximum XOR value obtainable by pairing any two numbers in the given list.

bit-manipulation xor array
+25 pts 30m
Bit Manipulation easy

Toggle kth Bit

Implement a function that toggles the kth bit of a non-negative integer (0-indexed from the least significant bit) and returns the new integer.

bit-manipulation xor binary
+10 pts 10m
Bit Manipulation easy

Subset XOR sum

Given a list of integers, compute the bitwise XOR of each non-empty subset and return the sum of those XOR totals.

xor bitwise subsets
+8 pts 10m
Binary Search medium

Single Element in Sorted Array

Given a sorted array where every element appears exactly twice except one which appears once, return the single element.

binary-search array xor
+20 pts 25m
Cryptography & Hashing easy

XOR Cipher Encode

Implement the XOR cipher: encode a string by XORing each character with a key character.

xor encryption strings
+10 pts 10m

Showing 1–10 of 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

  1. Pick a category — basics, algorithms, strings, and more
  2. Open a challenge, read the statement, and edit the starter code
  3. 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.