Multiplication Table Row
Return the nth row of a multiplication table as a list of 1..n products.
Custom Sort String
Given a string s and an order string, reorder s so that characters that appear in order come first in that order, and all other characters are appended in stable original order.
Generate a Multiplication Table
Build a function that returns an n x n multiplication table as a list of lists.
Radix Sort
Implement LSD radix sort to sort a list of non-negative integers in ascending order.
Default Argument Trap
Implement a function that safely accumulates items without the classic mutable default argument bug.
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.
Serialize dict to TOML-like
Convert nested Python dicts into a simplified TOML-like string with sorted keys, type-aware formatting, and flat table sections.
Inner Join Two Tables
Write a function that inner joins two lists of dictionaries on a common key and returns the combined rows.
Create Table Schema
Write a function that creates a SQLite table with a given name and columns, and returns the resulting schema as a list of column definitions.
Second highest salary
Given an employees table, write a SQL query that returns the second highest distinct salary, or NULL if it doesn't exist.
Nth Highest Salary
Write a Python function using SQLite to return the Nth highest distinct salary from an employee table.
Customers Never Order
Given Customers and Orders tables, return the names of customers with no orders, sorted alphabetically, or None if all have ordered.
Showing 12 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.