Rotate String Right
Implement a function that rotates a given string to the right by a specified number of positions, handling shifts larger than the string length.
Compress Consecutive Chars
Write a function that compresses a string by replacing runs of identical characters with the character followed by the count.
Expand compressed string
Implement a function that expands run-length encoded strings (e.g., 'a3b2' → 'aaabb').
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.
Sort characters in string
Write a function that sorts the characters in a string and returns the sorted string.
Most Common Character
Return the character that appears most frequently in a string, breaking ties by earliest occurrence.
Roman to Integer
Convert a valid Roman numeral string to an integer using standard rules.
Isomorphic Strings Check
Given two strings, check if they are isomorphic by verifying a one-to-one character mapping.
Index of First Occurrence
Implement a function that finds the starting index of a substring within a string, returning -1 when absent.
Safe Command Executor
Implement emulate_run that simulates running a command list and returns output and exit code.
Error message formatter
Write a function that constructs a formatted error message from a code, an optional context, and a fallback message.
Stack Trace Sanitizer
Implement a function that rewrites traceback file paths to basenames only.
Extract Hashtags
Extract unique hashtags from a given text string in the order they appear.
Extract mentions
Extract unique @mentions from a string, respecting email-like patterns and punctuation.
Validate time format
Check whether a given string is a valid 24-hour time in HH:MM format.
Parse Log Line
Write a function that parses a log line and returns a dictionary with timestamp, level, and message.
Replace multiple spaces
Implement a function that replaces every sequence of spaces with a single space.
Remove HTML tags
Remove all HTML tags from a string to extract clean text.
Extract Quoted Strings
Write a function that extracts the text inside every double-quoted substring from a given string.
Split on camelCase
Given a camelCase string, split it into words at uppercase letters and return them as lowercase words.
Extract domain from URL
Extract the domain (hostname without port or www) from a given URL string.
Normalize Whitespace
Write a function that normalizes any whitespace in a string to single spaces and trims the ends.
Strip Leading Zeros
Write a function that strips leading zeros from a string representing a non-negative integer.
Showing 145–168 of 556 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.