Stack class
Implement a Stack class with push, pop, peek, is_empty, and size.
Event emitter basics
Implement an EventEmitter class with subscribe/emit/unsubscribe functionality.
Rectangle class
Implement a Rectangle class with properties, methods, and special methods for basic geometry and comparison.
Queue class (list-based)
Implement a Queue class with enqueue, dequeue, peek, is_empty, and is_full methods using a list.
Abstract Base Class
Create an abstract Shape class and implement Rectangle and Circle subclasses with area and perimeter.
Observer pattern lite
Implement a simple Subject class supporting subscribe, unsubscribe, and notify observers.
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.
Singleton Factory
Implement a factory class that returns a singleton instance per key.
Playing card class
Design a PlayingCard class with suit, rank, color, and equality/comparison magic methods.
Valid parentheses
Return True if brackets in the string close in the correct order.
Binary search
Return the index of target in a sorted list, or -1 if not present.
Index of peak element
Implement a function that returns the index of any peak element in a given integer array.
Count pairs with given difference
Count how many unordered pairs in a list have a given absolute difference using an efficient approach.
Previous Smaller Element
Find the nearest previous index with a smaller value for every element in an array.
Pascal Triangle Row
Given a non-negative integer n, return the nth row of Pascal's triangle as a list of integers.
Employee Hierarchy
Build an employee hierarchy tree and compute the total number of direct and indirect reports for each employee.
Union Find Class
Implement a UnionFind class with find and union operations supporting path compression and union by size.
Bubble Sort
Implement bubble sort that sorts a list of numbers in ascending order.
Selection Sort Implementation
Implement selection sort to sort a list of numbers in ascending order.
Shell Sort
Implement Shell sort, an in-place comparison sort that generalizes insertion sort, using a gap sequence that shrinks by half each pass.
Exponential Search
Implement exponential search to find any valid index of a target in a sorted list.
Find Peak Index
Given a list of integers, return the index of any peak element where the value is not smaller than its neighbors.
Showing 289–312 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.