Fancy Index Select
Given a 2D matrix and a list of row indices, select those rows in order and return them as a new 2D list.
Reshape array dimensions
Implement a function that reshapes a 1D list into a 2D list with given dimensions.
Euclidean Distance Matrix
Write a function to compute the Euclidean distance between every pair of points from two lists.
Generate a Multiplication Table
Build a function that returns an n x n multiplication table as a list of lists.
Concatenate Horizontally
Write a function that horizontally concatenates two 2D lists into a new 2D list.
Clique Detection
Given an undirected graph and a list of vertices, check if every pair of distinct vertices in the list is connected by an edge.
Valid Sudoku Board
Determine if a 9x9 Sudoku board is valid by checking rows, columns, and 3x3 sub-boxes.
Rotate Image 90 Degrees Clockwise
Rotate a square matrix 90 degrees clockwise and return the rotated matrix.
Valid Sudoku Validator
Determine if a given 9x9 Sudoku board is valid by checking rows, columns, and 3x3 boxes.
Toeplitz Matrix Check
Write a function is_toeplitz(matrix) that checks if a 2D list is a Toeplitz matrix, where all elements on the same diagonal from top-left to bottom-right are identical.
Diagonal Traverse Matrix
Implement a function that returns all elements of a matrix in diagonal zigzag order.
Transpose Matrix In-Place
Implement a function that transposes a square matrix in-place and returns the transposed matrix.
Matrix Multiply 2D
Write a function that multiplies two 2D matrices (lists of lists) and returns the product matrix.
Transpose 2D Array
Implement a function that returns the transpose of a rectangular 2D list.
Flipping an Image
Implement a function that flips an image represented as a binary matrix by reversing each row and inverting each pixel.
Sum each matrix row
Given rows, return each row sum.
Sum each matrix column
Return column totals for a rectangular matrix.
Showing 1–17 of 17 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.