Set symmetric difference
Write a function that returns the elements found in exactly one of two sets, sorted ascending.
Remove Duplicates from Sorted Array
Given a sorted list, remove duplicates in-place and return the new length.
Sort characters alphabetically
Sort all characters in a string alphabetically and return the sorted string.
Sort characters in string
Write a function that sorts the characters in a string and returns the sorted string.
Remove duplicates (sorted)
Return a sorted list with duplicates removed.
Merge two sorted arrays
Merge two sorted arrays into one sorted array.
Insert into a Sorted List
Implement a function that inserts a value into a sorted list at the correct position using binary search.
Intersection of Two Lists
Given two lists, return a sorted list of unique elements that appear in both lists.
Merge Sorted Array In Place
Write a function that merges two sorted arrays into the first array in-place, keeping the result sorted.
Cartesian Product Pairs
Create a function that returns the Cartesian product of two lists as a sorted list of lists.
List intersection
Return the sorted list of elements common to both lists.
Keys Sorted by Value Descending
Given a dictionary mapping strings to integers, return a list of keys sorted by value descending, and when values tie, alphabetically ascending.
Anagram Dictionary Groups Lite
Group a list of words into anagrams using a dictionary keyed by sorted characters.
Common Keys of Two Dictionaries
Implement a function that finds keys shared by two dictionaries and returns them sorted.
Union of Many Sets
Implement a function that takes any number of sets and returns a sorted list of their union.
Anagram Groups by Size
Group a list of words into anagram groups and return them sorted by group size and lexicographically.
Top K Frequent Words
Given a list of words, return the k most frequent words sorted by frequency (descending) and then alphabetically.
Symmetric Difference
Write a function that computes the symmetric difference of two lists, returning a sorted list of unique elements.
Revenue by Month
Write a function that groups a list of (date, amount) pairs by year-month and returns total revenue per month as a sorted dictionary.
Binary search
Return the index of target in a sorted list, or -1 if not present.
Exponential Search
Implement exponential search to find any valid index of a target in a sorted list.
Merge Two Sorted Lists
Write a function that merges two sorted lists into a single sorted list.
Jump Search
Implement the jump search algorithm to locate a target in a sorted list, returning its index or -1.
Sieve of Eratosthenes
Implement the Sieve of Eratosthenes to return a sorted list of all primes up to a given integer n.
Showing 1–24 of 33 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.