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875 challenges 536 easy 303 medium 36 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

Dicts & Sets medium

Subarray sum equals K

Count the number of contiguous subarrays whose sum equals k.

prefix-sum dict arrays

Data Structures & Algorithms medium

Arithmetic Slices Count

Given a list of integers, count how many contiguous subarrays of length at least 3 form an arithmetic sequence.

arrays arithmetic counting

Binary Search medium

Binary Search on Answer: Find the Minimal Maximum Subarray Sum

Implement a function that finds the minimal possible maximum subarray sum when splitting an array into at most k contiguous subarrays.

binary-search arrays greedy

Two Pointers & Sliding Window medium

Count Nice Subarrays

Given an array of integers, count the number of contiguous subarrays that contain exactly k odd numbers.

sliding-window two-pointers subarray

Two Pointers & Sliding Window medium

Binary Subarray with Sum

Given a binary list and a goal sum, count the number of subarrays that add up to that goal.

sliding-window two-pointers subarray

Two Pointers & Sliding Window medium

Subarray product less than K

Count contiguous subarrays where the product of all elements is strictly less than a target K.

sliding-window two-pointers subarray

Two Pointers & Sliding Window medium

Count Nice Subarrays

Count subarrays that contain exactly k odd numbers.

sliding-window two-pointers counting

Stacks & Queues medium

Sum of Subarray Minimums

Given an integer array, sum the minimum of all contiguous subarrays modulo 10^9+7.

stack array monotonic-stack

Showing 8 challenges · medium

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.