Practice Arena

Python Coding
Challenges

Write real Python in the browser. Instant feedback. From beginner to expert.

925 challenges 556 easy 323 medium 46 hard

All Easy Medium Hard

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

Lists & Arrays medium

Flatten nested list

Yield every integer from an arbitrarily nested list, depth-first.

recursion generators

Lists & Arrays easy

Flatten Multidimensional Lists

Write a function that flattens arbitrarily nested lists of integers into a single list.

recursion nested-lists flatten

Dicts & Sets easy

Union of Many Sets

Implement a function that takes any number of sets and returns a sorted list of their union.

sets union flatten

Iterators & Generators easy

Yield from delegation

Implement a generator that flattens nested iterables of any depth using `yield from`.

generators yield delegation

Iterators & Generators easy

Flatten Nested List Iterator

Implement a class that iterates over all integers in a nested list structure in depth-first order.

iterator generator flatten

Matrix & 2D Arrays medium

Shift 2D Grid

Implement a function to shift a 2D grid right by k positions, flattening the grid and wrapping elements.

grid list modulo

Data Formats & Parsing medium

Flatten nested JSON

Write a function that flattens nested JSON objects into a flat dictionary with dot-separated keys, handling lists and empty objects.

json recursion dictionaries

Data Formats & Parsing medium

Unflatten JSON dict

Given a flat dictionary with keys like 'a.b.c', reconstruct the nested dictionary where each dotted segment becomes a nested level.

json dict parsing

Numpy & Vectorized Computing medium

Flatten matrix to vector

Read rows left-to-right, top-to-bottom.

vectors arrays numpy-style

Showing 1–9 of 9 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.