Find Missing Number
Given a list of n distinct integers from 0..n with one missing, return the missing number.
Parse URL components
Write parse_url that splits a URL into its standard components with defaults for missing parts.
Find Missing Number 1 to n
Given a list containing n-1 distinct integers from 1 to n, find the missing number without using extra space.
Two Missing Numbers
Given a list of n-2 unique integers from 1 to n, find the two missing numbers efficiently.
Three Missing Numbers
Find the three missing numbers from a shuffled list containing all but three integers from 1 to n.
Missing keys default zero
Write a function to sum numeric values from dictionaries, treating missing keys as zero.
Nested get with dotted path
Implement a function that safely retrieves a value from a deeply nested dictionary using a dot-separated path, returning a default if any key is missing.
Key error handler
Implement a safe dictionary access function that returns a default value on missing keys.
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.
Kth Missing Positive
Given a strictly increasing array and an integer k, return the k-th positive integer that is missing from the array.
Showing 1–10 of 10 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.