Udemy - Build Your Own Regex Engine from Scratch in Python - 2/2026

[Knight]

Requirements
Basic to intermediate knowledge of Python
Familiarity with programming fundamentals such as functions and classes
General understanding of strings and control flow
Curiosity to learn how things work internally
No prior knowledge of compiler design or regex internals is required
Description
Regular Expressions are often seen as confusing and hard to master. Most tutorials teach you how to use regex, but very few explain how regex actually works internally.

In this course, you will go beyond writing regex patterns and instead build a complete Regular Expression Engine from scratch in Python. This hands-on project will help you truly understand how regex patterns are processed, parsed, and matched behind the scenes.

Rather than focusing on memorizing syntax, this course focuses on understanding the mechanics of a regex engine, similar in behavior to Python’s re module.

What This Course Is About

This is a deep-dive, implementation-based course where you will:

Design and implement a Lexer (Tokenizer) for regex patterns

Understand how regex patterns are broken into tokens

Build a Parser using recursive descent parsing

Construct an Abstract Syntax Tree (AST) to represent regex structure

Implement a Matcher Engine that evaluates patterns against input strings

Support core regex features such as:

Character classes

Quantifiers

Alternation

Capturing and non-capturing groups



Implement matching functions similar to:

match

search

findall

By the end of the course, regex will no longer feel like magic. You will understand exactly how a regex engine reads patterns and matches text step by step.

Why This Course Is Different

Most regex courses focus only on usage. This course focuses on how regex engines are built.

You will not just learn what regex does — you will learn why it behaves the way it does.

This approach is ideal for:

Developers who want a deeper understanding of regex

Programmers interested in compiler-like concepts

Anyone curious about lexers, parsers, and pattern matching engines

This is one specific implementation of a regex engine, similar to Python’s re module. Other approaches exist (such as Thompson’s NFA), but this course focuses on an approach that supports advanced features like backtracking and grouping.

Who this course is for:
Python developers who want to understand regex beyond basic usage
Programmers curious about how regex engines are built
Computer science students interested in parsing and pattern matching
Developers who want hands-on experience with lexer and parser concepts
Anyone who finds regex confusing and wants to truly understand how it works​

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