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

Lists & Arrays easy

Merge two sorted arrays

Merge two sorted arrays into one sorted array.

arrays merge two-pointer

Lists & Arrays medium

Merge intervals

Merge all overlapping intervals and return a sorted result.

Lists & Arrays easy

Interleave Two Lists

Write a function that interleaves two lists element by element, preserving order.

lists merge indexing

Lists & Arrays medium

Count Smaller Numbers

Given an integer list, return for each position how many later elements are smaller than it.

arrays counting merge-sort

Lists & Arrays easy

Merge Sorted Array In Place

Write a function that merges two sorted arrays into the first array in-place, keeping the result sorted.

arrays sorting in-place

Lists & Arrays easy

Sort List Merge Sort

Write a function that sorts a list of integers using the merge sort algorithm.

merge sort sorting recursion

Showing 1–6 of 6 challenges · 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.