Count trailing zeros
Write a function that counts the number of trailing zeros in the decimal representation of a positive integer.
Integer to Roman
Convert a positive integer to its Roman numeral representation.
Strip Leading Zeros
Write a function that strips leading zeros from a string representing a non-negative integer.
Deck of Cards Class
Implement a Deck class representing a standard 52-card deck with shuffle, deal, and len support.
String Representation Mixin
Implement a mixin class that provides generic __repr__ and __str__ based on instance attributes.
Dataclass with slots
Implement a slotted frozen dataclass representing a 2D point with total ordering.
Count Set Bits
Implement a function that returns the number of set bits (1s) in the binary representation of a non-negative integer.
Gray Code Encode
Implement a function that converts a non-negative integer to its Gray code representation using bitwise XOR and shift.
Compress Bits Run
Write a function that compresses a binary string by representing consecutive identical bits as a count-bit pair.
Sparse Number Check
Check if a non-negative integer is sparse, meaning its binary representation contains no adjacent 1 bits.
Odd Parity Bit
Given an integer, return the odd parity bit (0 or 1) so that total number of 1-bits in the 8-bit representation becomes odd.
Letter Combinations of a Phone Number
Given a string of digits, return all possible letter combinations that the number could represent on a phone keypad.
Patching Array
Given a sorted array of positive integers and a target n, find the minimum number of patches to make every number from 1 to n representable as a subset sum.
Trapping Rain Water
Given an array of non-negative integers representing an elevation map, compute how much water it can trap after raining.
Fruit into Baskets
Given an array of integers representing fruit types, return the maximum number of fruits you can collect in a contiguous subarray with at most two distinct types.
Trapping Rain Water (Two Pointers)
Given an array of non-negative integers representing elevation heights, compute how much water can be trapped after rain.
Showing 16 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.