Find all indexes of a substring
Write a function that returns a list of all starting indexes where a substring appears in a string, including overlapping occurrences.
Find substring index
Implement a function that returns the starting index of the first occurrence of a substring using only basic string indexing and slicing.
Count Substrings
Implement a function that counts non-overlapping occurrences of a substring in a given string.
Index of First Occurrence
Implement a function that finds the starting index of a substring within a string, returning -1 when absent.
Extract Quoted Strings
Write a function that extracts the text inside every double-quoted substring from a given string.
ROT13 Transform
Implement ROT13, a letter substitution cipher that rotates the alphabet by 13 positions.
Abstract Base Class
Create an abstract Shape class and implement Rectangle and Circle subclasses with area and perimeter.
Lowest Common Ancestor in a Binary Search Tree
Implement a function to find the lowest common ancestor of two node values in a binary search tree.
Non-greedy quantifier
Implement a function that uses a non-greedy regex to extract the shortest substring between two delimiters.
Insert into BST
Implement insertion into a Binary Search Tree while maintaining BST properties.
Range Sum BST
Return the sum of all node values in a BST that lie within a given inclusive range [low, high].
Longest Substring Without Repeating Characters
Implement a function that returns the length of the longest substring without repeating characters.
Showing 1–12 of 12 challenges · easy
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.