Practice Arena

Python Coding
Challenges

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

467 challenges 330 easy 120 medium 17 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

Lists & Arrays easy

Running Product of Integers

Given a list of integers, return a new list where each element at index i is the product of all elements from index 0 to i.

prefix product lists

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

Wave sort array

Given a list of integers, reorder it into a wave pattern where elements alternate down-up, and return the new list.

sorting swap rearrangement

Lists & Arrays easy

Counting Sort

Implement the counting sort algorithm to sort a list of non-negative integers in O(n + k) time.

sorting counting arrays

Showing 4 challenges · easy · Lists & Arrays

Lists & Arrays — Python coding challenges

What you will find here

This page lists lists & arrays challenges — real Python problems you solve in the browser IDE with instant test feedback. Each challenge includes a clear brief, starter code, and automated checks.

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.