Learn fundamentals

Short quizzes that build the mental models behind the language. No hand-holding - answer, see why, move on.

Python

Variables, functions, classes, decorators, regex, type hints, and more — the mechanics that trip people up when it matters.

16 topics192+ questions

SQL

SELECT, filtering, joins, aggregation, window functions, and the NULL edge cases that catch everyone off guard.

17 topics170+ questions

Recommended order

Each topic builds on the one before. Start at step 1 and work down.

Python

Foundation

Variables & Types

where everything starts

if / for / while

Intermediate

Python's superpower

Iterators & Generators

lazy evaluation, memory efficiency

Advanced

Classes

Functional Tools

map, filter, lambda, partial

Decorators

wrapping functions, @wraps, factories

pathlib, csv, json

Optional, TypedDict, Protocol

SQL

Foundation

SELECT Basics

where everything starts

WHERE clause

COUNT, SUM, AVG

GROUP BY

HAVING

Core

most tested concept

cleaner than nested subqueries

CASE Expressions

Set Operations

UNION, INTERSECT, EXCEPT

Advanced

Window Functions

hardest topic, do last