Practice Arena

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
Math & Number Theory easy

Happy number check

Implement a function that returns True if a number is happy, False otherwise.

math loops set
+8 pts 12m
Math & Number Theory medium

Correlation Coefficient

Write a pure-Python function that computes the Pearson correlation coefficient between two lists of numbers.

statistics math arrays
+15 pts 15m
Math & Number Theory easy

Z score normalization

Compute the z-scores for a list of numbers using the population standard deviation.

statistics math standard-deviation
+8 pts 10m
Bit Manipulation easy

Missing Number XOR

Given a list of n distinct numbers from 0 to n with one missing, use XOR to find and return the missing number.

xor bitwise arrays
+10 pts 15m
Bit Manipulation medium

Bitwise AND of a Range

Given a range [a, b], return the bitwise AND of all integers in that inclusive range without iterating over all numbers.

bitwise range optimization
+20 pts 15m
Bit Manipulation medium

Maximum XOR Pair

Implement max_xor_pair(nums) that returns the maximum XOR value obtainable by pairing any two numbers in the given list.

bit-manipulation xor array
+25 pts 30m
Trees & Binary Trees medium

Sum Root to Leaf Numbers

Given the root of a binary tree, compute the total sum of all root-to-leaf numbers.

binary-tree dfs recursion
+25 pts 25m
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
+25 pts 25m
Two Pointers & Sliding Window medium

Closest Three Sum

Given an array of integers and a target, return the sum of three numbers that is closest to the target.

sorting two-pointers array
+20 pts 20m
Two Pointers & Sliding Window medium

Count Nice Subarrays

Count subarrays that contain exactly k odd numbers.

sliding-window two-pointers counting
+25 pts 30m
Datetime & Time Calculations medium

Julian Day Number Converter

Implement two functions to convert between Gregorian calendar dates and Julian Day Numbers using a standard formula.

datetime date-arithmetic algorithms
+20 pts 20m
Data Formats & Parsing medium

Extract JSON-like numbers

Parse a simplified JSON-like string without using the json module and sum all numbers found in it.

json parsing numbers
+14 pts 20m

Showing 49–60 of 60 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

  1. Pick a category — basics, algorithms, strings, and more
  2. Open a challenge, read the statement, and edit the starter code
  3. 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.