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Python Coding
Challenges

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925 challenges 556 easy 323 medium 46 hard

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All Python Basics Strings & Text Lists & Arrays Dicts & Sets Functions & Closures OOP & Classes Data Structures & Algorithms Advanced Python Iterators & Generators Decorators & Context Managers Error Handling & Exceptions Regular Expressions Math & Number Theory Bit Manipulation Dynamic Programming Trees & Binary Trees Graphs & Graph Algorithms Recursion & Backtracking Greedy Algorithms Binary Search Two Pointers & Sliding Window Stacks & Queues Heaps & Priority Queues Linked Lists Matrix & 2D Arrays Datetime & Time Calculations Data Formats & Parsing SQL & SQLite Numpy & Vectorized Computing Cryptography & Hashing

Python Basics easy

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.

lists search indexing

Python Basics easy

Cycle a List Once

Implement a function that rotates a list right by one position.

lists rotation indexing

Python Basics easy

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.

indexing lists matrix

Strings & Text easy

Find all indexes of a substring

Write a function that returns a list of all starting indexes where a substring appears in a string, including overlapping occurrences.

substring string searching

Strings & Text easy

Interleave Two Strings

Given two strings s1 and s2, return a new string that interleaves them character by character, starting with s1.

strings merging loops

Strings & Text easy

Find substring index

Implement a function that returns the starting index of the first occurrence of a substring using only basic string indexing and slicing.

string search index

Lists & Arrays easy

Rotate Left by k

Implement a function that rotates a list left by k positions.

rotation lists slicing

Lists & Arrays easy

Interleave Two Lists

Write a function that interleaves two lists element by element, preserving order.

lists merge indexing

Lists & Arrays easy

Keep only even indexes

Given a list, return a new list containing only the elements at even indices (0, 2, 4, ...).

list slicing indexing

Lists & Arrays easy

Middle Element of an Odd-Length List

Implement a function that returns the middle element of an odd-length list.

lists indexing basic

Lists & Arrays easy

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.

lists indexing search

Lists & Arrays easy

Image channel swap

Implement a function that swaps the red and blue channels of an RGB image.

lists comprehensions rgb

Dicts & Sets easy

Word to Index Map

Create a function that returns a dictionary mapping each unique word to the index of its first occurrence.

dictionary mapping indexing

Showing 1–13 of 13 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.