Python coding challenges: "aggregation"

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Dicts & Sets easy

Revenue by Month

Write a function that groups a list of (date, amount) pairs by year-month and returns total revenue per month as a sorted dictionary.

dict aggregation sales

+8 pts 10m

Dicts & Sets easy

Pivot sales by product

Write a function that pivots sales records into a dictionary keyed by product with monthly totals.

dicts grouping aggregation

+10 pts 15m

SQL & SQLite easy

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.

sql sqlite query

+8 pts 10m

SQL & SQLite medium

Nth Highest Salary

Write a Python function using SQLite to return the Nth highest distinct salary from an employee table.

sql sqlite aggregation

+20 pts 20m

Showing 4 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.

Python Coding Challenges