The Regex Field Guide

Preview

What it teaches

The regular-expression basics, checked in Python: the special characters, classes like [a-z] and \d, repeats (* + ? {m,n}), anchors (^ $ \b), alternation with | and brackets, greedy vs lazy matching, and what findall, sub and split give back. You say which strings a pattern matches, predict what a call returns, and write patterns that match exactly what’s asked. The AI asks 3 questions, places you, shows a short card per module, then gives you one item at a time and checks you against an answer key: every answer about what a pattern matches or returns came from running it in Python.

Answers use Python’s re. Tested on JavaScript (Node 25): the patterns here give the same matches on this course’s strings, with four differences: fullmatch needs ^ and $ in JavaScript, findall with groups returns whole matches there, $ matches just before a final newline only in Python, and the letter class matches accented letters only in Python. Java, editors, spreadsheets and grep were not tested.

How long

34 items. About 40-50 rounds from scratch (about 15 if you already know the basics) plus a 12-item final: 2-3 sessions (estimate, not timed with a real student). The tutor gives a one-line save code at the end of each session.