Classify triangle by sides
Write a function that classifies a triangle based on three side lengths.
Validate date format
Return True if input string is exactly YYYY-MM-DD and a real calendar date.
Invariant checker
Implement check_invariant(a, b, c) that returns True when a equals b plus c and False otherwise, matching the given examples.
Validate Password Strength
Implement a function that validates password strength based on clear rules.
Is isogram
Implement a function that determines whether a string is an isogram (no repeated letters, case-insensitive).
Is pangram?
Implement is_pangram(s) to return True if the string contains every letter from 'a' to 'z' at least once, ignoring case and non-alphabetic characters.
Mask email address
Given an email address, return a masked version that hides everything but the first and last character of the local part and the domain.
Is isogram?
Write a function that checks whether a given word is an isogram, ignoring letter case and only considering alphabetic characters.
Validate time format
Check whether a given string is a valid 24-hour time in HH:MM format.
Validate username format
Implement a function that validates a username according to length, allowed characters, and no consecutive underscores.
Minimum Remove Valid Parentheses
Given a string with parentheses and letters, remove the fewest parentheses to make it valid.
Additive number sequence
Check whether a given digit string can be partitioned into a valid additive sequence where each term is the sum of the previous two.
Class-based decorator with call validation
Build a class-based decorator that validates a single argument's type and logs successful invocation.
Safe int parser
Implement safe_parse_int that converts a string to an int, returning a default value on failure.
Safe Float Parser
Write a function that safely converts a string to a float, returning None for invalid inputs.
Validation result object
Implement a ValidationResult class that tracks validation errors and can report validity.
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.
Lookahead Validation
Write a regex-based function to check if a password meets length and character class requirements.
Match Balanced Parentheses with Regex
Write a function that uses regular expressions to determine if parentheses are balanced and properly nested.
Showing 1–24 of 33 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.