Practice Arena

Python Coding
Challenges

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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

Strings & Text easy

Repeat each character n times

Given a string s and an integer n, return a new string where each character of s is repeated n times consecutively.

strings join comprehension

Strings & Text easy

Normalize Whitespace

Write a function that normalizes any whitespace in a string to single spaces and trims the ends.

strings whitespace split-join

Dicts & Sets easy

Disjoint Set Check

Check if two lists are disjoint by verifying they have no common elements.

sets list membership

Data Structures & Algorithms easy

Union Find Class

Implement a UnionFind class with find and union operations supporting path compression and union by size.

union-find disjoint-set data-structures

Two Pointers & Sliding Window medium

Interval List Intersections

Given two lists of sorted, disjoint intervals, return the list of intersections between them.

two-pointers intervals merging

Linked Lists hard

Join node values with arrows

Format string node values as 'a -> b -> c'; empty list returns ''.

linked-list lists pointers

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

Customers Never Order

Given Customers and Orders tables, return the names of customers with no orders, sorted alphabetically, or None if all have ordered.

sql sqlite join

Showing 1–8 of 8 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.