Parse table rows
Implement a function that converts a simple text table into a list of dictionaries.
Inner Join Two Tables
Write a function that inner joins two lists of dictionaries on a common key and returns the combined rows.
Create Table Schema
Write a function that creates a SQLite table with a given name and columns, and returns the resulting schema as a list of column definitions.
Second highest salary
Given an employees table, write a SQL query that returns the second highest distinct salary, or NULL if it doesn't exist.
Customers Never Order
Given Customers and Orders tables, return the names of customers with no orders, sorted alphabetically, or None if all have ordered.
Cumulative Sum SQL
Write a SQL query to compute cumulative sales totals per product ordered by sale date.
Select All Users
Write a function that connects to an in-memory SQLite database and returns all users as a list of lists.
Add column alter
Write a function that connects to an in-memory SQLite database, creates a table, inserts rows, and adds a new column with ALTER TABLE.
Element-wise vector addition
Add equal-length numeric lists element-wise.
Scale a vector by scalar
Multiply every element by k.
Dot product of two vectors
Return sum of element-wise products.
Mean of a vector
Return arithmetic mean or 0.0 when empty.
Maximum element in vector
Return largest value or None when empty.
Minimum element in vector
Return smallest value or None when empty.
Clip vector to range
Clamp each value to [lo, hi].
Min-max normalize vector
Scale values to 0..1; equal values become all 0.0.
Sum each matrix row
Given rows, return each row sum.
Sum each matrix column
Return column totals for a rectangular matrix.
SHA256 Hash String
Write a function that returns the SHA256 hexadecimal digest of a given string.
Compute SHA-1 Hash String
Write a function that returns the SHA-1 hash of a string as a 40-character hex string.
Constant Time Compare
Write a function that compares two strings without leaking length or content via timing.
Verify HMAC signature
Implement a function that verifies an HMAC-SHA256 signature for a message and key.
Password Salt Hash
Implement a function that returns a secure salted SHA-256 password hash with a deterministic format.
SHA1 Hash String
Implement a function that returns the SHA1 hexadecimal digest of an input string.
Showing 529–552 of 556 challenges · easy
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.