Understanding Python re(gex)?

32 ratings


Scripting and automation tasks often need to extract particular portions of text from input data or modify them from one format to another.

This book will help you learn Python Regular Expressions, a mini-programming language for all sorts of text processing needs.

The book heavily leans on examples to present features of regular expressions one by one. It is recommended that you manually type each example and experiment with them.

Both the standard re module and the popular third-party regex module are covered in this book.

Exercises are also included to test your understanding.

Promo video


You should be familiar with programming basics. You should also have a working knowledge of Python syntax and features like string formats, string methods and list comprehensions.

You are also expected to get comfortable with reading manuals, searching online, visiting external links provided for further reading, tinkering with illustrated examples, asking for help when you are stuck and so on. In other words, be proactive and curious instead of just consuming the content passively.

If you have prior experience with a programming language but not Python, see my curated list of learning resources before starting this book.


I love your books on regex...As a student from the Digital VLSI space, it is indeed useful now and definitely in the future. It's really well written and really easy to understand the examples — feedback on reddit

Sample chapters

For a preview of the book, see sample chapters on GitHub.

GitHub repo

Visit https://github.com/learnbyexample/py_regular_expressions for markdown source, example files, exercise solutions and other details related to the book.

Interactive exercises

Based on the book contents as well as the exercises, I made an interactive TUI app with 100+ questions covering both the builtin re module and the third-party regex module. These exercises will test your understanding of anchors, alternation, grouping, escaping metacharacters, dot metacharacter, quantifiers, character class, lookarounds, flags, etc.


  1. Preface
  2. Why is it needed?
  3. re introduction
  4. Anchors
  5. Alternation and Grouping
  6. Escaping metacharacters
  7. Dot metacharacter and Quantifiers
  8. Interlude: Tools for debugging and visualization
  9. Working with matched portions
  10. Character class
  11. Groupings and backreferences
  12. Interlude: Common tasks
  13. Lookarounds
  14. Flags
  15. Unicode
  16. regex module
  17. Gotchas
  18. Further Reading

Feedback and Errata

I would highly appreciate if you'd let me know how you felt about this ebook. It could be anything from a simple thank you, Gumroad rating, pointing out a typo, mistakes in code snippets, which aspects of the book worked for you (or didn't!) and so on. Reader feedback is essential and especially so for self-published authors.

You can reach me via:

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Understanding Python re(gex)?

32 ratings
I want this!