Parse JSON safely
Implement a robust JSON string parser that returns a fallback on invalid input.
Parse Error Recovery
Parse a whitespace-separated string into a list of valid integers, skipping invalid tokens.
Validate Email Regex
Implement a function that validates email addresses using regex with specific rules.
Validate phone number
Write a function that uses regular expressions to determine if a given string is a valid US phone number.
Match IPv4 Address
Write a function that uses a regular expression to check if a string is a valid IPv4 address.
Match IPv6 Address
Write a function that uses a regex to validate whether a string is a fully expanded IPv6 address.
Match Credit Card Pattern
Write a function that validates a credit card number string against a set of formatting rules.
Validate Hex Color Code
Write a function that validates hex color codes using regular expressions.
Multiline anchor match
Extract lines beginning with a plain-text prefix from multiline strings using Python's re module.
Match Balanced Parentheses with Regex
Write a function that uses regular expressions to determine if parentheses are balanced and properly nested.
Match scientific notation
Implement a function that checks if a string is in valid scientific notation.
Non-greedy quantifier
Implement a function that uses a non-greedy regex to extract the shortest substring between two delimiters.
Compress Bits Run
Write a function that compresses a binary string by representing consecutive identical bits as a count-bit pair.
Levenshtein Distance
Implement the classic Levenshtein distance algorithm to measure string similarity.
Longest Common Subsequence
Given two strings, compute the length of the longest subsequence common to both.
Longest Palindromic Subsequence
Compute the length of the longest palindromic subsequence in a given string.
Edit Distance (Levenshtein Distance)
Implement the classic edit distance algorithm to find the minimum number of single-character edits required to transform one string into another.
Word Break DP
Implement a function to check if a string can be segmented into space-separated dictionary words.
Palindrome Partitioning Minimum Cuts
Given a string, return the minimum number of cuts needed such that every substring in the partition is a palindrome.
Shortest Common Supersequence
Given two strings, return any shortest supersequence that contains both as subsequences.
Interleaving string
Given three strings s1, s2, and s3, check if s3 is formed by interleaving s1 and s2 while preserving the order of each input string.
Alien Dictionary Order
Given a sorted list of words in an alien language, derive the order of its unique letters.
Open the Lock BFS
Implement a BFS solution to find the minimum number of turns needed to open a 4-wheel lock, avoiding a set of deadends.
Minimum Genetic Mutation
Implement a function to compute the minimum number of single-character mutations needed to transform one gene string into another, using a given bank of valid mutations.
Showing 145–168 of 219 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.