• views: 121
• date: 2 February 2026
• posted by: voska89

Understand How Regular Expressions Really Work Using Lexer, Parser & Tokenization, Parsing, AST & Pattern
What you'll learn
✓ Understand how regular expression engines work internally
✓ Learn how regex patterns are tokenized using a lexer
✓ Design and implement a tokenizer for regex syntax
✓ Build a recursive descent parser for regex patterns
✓ Create an Abstract Syntax Tree (AST) to represent regex structure
✓ Understand core regex features like quantifiers, alternation, and groups
✓ Implement a complete regex matching engine in Python
✓ Build functions similar to match, search, and findall
✓ Gain deep insight into how regex works under the hood
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
Homepage

https://www.udemy.com/course/build-your-own-regex-engine-from-scratch-in-python/

   
   
   

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