Substring Anagrams
Return all start indices in a string where a substring of length k is an anagram of a pattern string.
Hash map merge
Write a function that merges two dictionaries recursively, combining values and preserving structure.
Class Method Factory
Create a class method factory that dynamically adds methods to a class based on a mapping of names to behaviors.
Decode Ways
Count the number of ways to decode a numeric string into letters using the mapping A=1 to Z=26.
Longest Arithmetic Subsequence
Given a list of integers, return the length of the longest arithmetic subsequence (constant difference) within it.
Character Replacement Window
Given a string and a number k, find the length of the longest substring that can be made uniform by replacing at most k characters.
Permutation in String
Determine if any permutation of a shorter string appears as a contiguous substring in a longer string using an efficient sliding window.
Top K Frequent Elements
Given an integer array and a number k, return the k most frequent elements using a heap-based approach.
Showing 8 challenges · medium
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.