Count down from n
Implement a function that returns a list from n down to 1.
Multiplication Table Row
Return the nth row of a multiplication table as a list of 1..n products.
Last Occurrence of a Value
Implement a function that returns the last index of a given value in a list, or -1 if it's not present.
Cycle a List Once
Implement a function that rotates a list right by one position.
Boolean Mask Filter
Write a function that filters a list based on a boolean mask and returns the selected elements.
Replace negatives with zero
Implement a function that replaces all negative numbers in a list with zero.
Average of a list
Write a function that computes the average of a list of numbers, handling empty lists by returning 0.
Map, Filter, Reduce
Implement three functions using map, filter, and reduce to manipulate a list of integers.
Count Leading Zeros
Write a function that returns the number of leading zeros in a list of integers.
Safe Command Executor
Implement emulate_run that simulates running a command list and returns output and exit code.
Running Product of Integers
Given a list of integers, return a new list where each element at index i is the product of all elements from index 0 to i.
Move Zeros to the End
Reorder a list in-place, pushing all zeros to the end while preserving the order of non-zero numbers.
Chunk a list into n-sized parts
Write a function that divides a list into sublists of at most n elements.
Rotate Left by k
Implement a function that rotates a list left by k positions.
Interleave Two Lists
Write a function that interleaves two lists element by element, preserving order.
Running Maximum
Implement a function that returns a list where each element is the largest value seen so far.
Insert into a Sorted List
Implement a function that inserts a value into a sorted list at the correct position using binary search.
Average excluding min and max
Return the average of a list after discarding the lowest and highest elements, handling edge cases.
Zip lists into pairs
Write a function that takes two lists and returns a list of two-element sublists pairing elements by index up to the shortest length.
Longest Run of Equal Values
Compute the length of the longest run (consecutive block) of equal elements in a list.
Middle Element of an Odd-Length List
Implement a function that returns the middle element of an odd-length list.
Is Subset of Another List
Write a function that returns True if every element in a given list exists in another list, ignoring duplicates.
Unzip pairs into two lists
Write a function that takes a list of pairs and returns two separate lists: first elements and second elements.
Generate a Multiplication Table
Build a function that returns an n x n multiplication table as a list of lists.
Intersection of Two Lists
Given two lists, return a sorted list of unique elements that appear in both lists.
Union of Two Lists
Implement a function that combines two lists and returns only unique elements.
Difference of Two Lists
Write a function that returns items in list a that are not in list b, preserving order and duplicates.
Chunk list into groups
Implement a function that splits a list into sublists of a given size.
Zip Two Lists
Write a function that pairs elements from two lists by index, stopping at the shorter list.
Last occurrence index
Implement a function that returns the last index of a given value in a list, or -1 if the value is not present.
List intersection
Return the sorted list of elements common to both lists.
Are two lists the same multiset
Write a function that checks if two lists contain the same elements with the same multiplicities, ignoring order.
Sort by frequency
Sort a list by element frequency descending, with ties broken by order of first occurrence.
Set intersection size
Count how many distinct values appear in both of two given lists.
Symmetric Difference
Write a function that computes the symmetric difference of two lists, returning a sorted list of unique elements.
Disjoint Set Check
Check if two lists are disjoint by verifying they have no common elements.
Selection Sort Implementation
Implement selection sort to sort a list of numbers in ascending order.
Pairwise Sequence Pairs
Write a generator function pairwise that yields each consecutive overlapping pair from any iterable as lists.
Triangle Minimum Path
Compute the minimum path sum from top to bottom of a triangle given as a list of lists.
Showing 39 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.