Understanding Python re(gex)?

Learn Python Regular Expressions step-by-step from beginner to advanced levels with hundreds of examples and exercises. The standard library re and the third-party regex module are covered in this book. Visit https://youtu.be/2x2n7ynamm8 for a short video about the book.

The book also includes exercises to test your understanding, which are presented together as a single file in this repo — Exercises.md

For solutions to the exercises, see Exercise_solutions.md.

You can also use this interactive TUI app to practice most of the exercises from the book.

See Version_changes.md to keep track of changes made to the book.

E-book

• You can purchase the pdf/epub versions of the book using these links
  • https://learnbyexample.gumroad.com/l/py_regex
  • https://leanpub.com/py_regex
• You can also get the book as part of these bundles:
  • All books bundle bundle from https://learnbyexample.gumroad.com/l/all-books
    • Includes all my programming books
  • Learn by example Python bundle from https://leanpub.com/b/python-bundle or https://learnbyexample.gumroad.com/l/python-bundle
  • Awesome Regex bundle from https://leanpub.com/b/regex or https://learnbyexample.gumroad.com/l/regex
  • The Indie Python Extravaganza bundle from https://leanpub.com/b/theindiepythonextravaganza
    • Includes Python 101, Pydon'ts, Python re(gex)?, Practice Python Projects and Clean Architectures in Python
  • Python 101 + Python re(gex)? or Python 201: Intermediate Python + Python re(gex)?
    • Python 101/201 is authored by Michael Driscoll
• See https://learnbyexample.github.io/books/ for list of other books

For a preview of the book, see sample chapters

The book can also be viewed as a single markdown file in this repo. See my blogpost on generating pdfs from markdown using pandoc if you are interested in the ebook creation process.

For the web version of the book, visit https://learnbyexample.github.io/py_regular_expressions/

Testimonials

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

Feedback and Contributing

⚠️ ⚠️ Please DO NOT submit pull requests. Main reason being any modification requires changes in multiple places.

I would highly appreciate it if you'd let me know how you felt about this book. It could be anything from a simple thank you, 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:

• Issue Manager: https://github.com/learnbyexample/py_regular_expressions/issues
• E-mail: echo 'bGVhcm5ieWV4YW1wbGUubmV0QGdtYWlsLmNvbQo=' | base64 --decode
• Twitter: https://twitter.com/learn_byexample

Table of Contents

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

Acknowledgements

• Python documentation — manuals and tutorials
• /r/learnpython/, /r/Python/ and /r/regex/ — helpful forums for beginners and experienced programmers alike
• stackoverflow — for getting answers to pertinent questions on Python and regular expressions
• tex.stackexchange — for help on pandoc and tex related questions
• canva — cover image
• Warning and Info icons by Amada44 under public domain
• oxipng, pngquant and svgcleaner — optimizing images
• David Cortesi for helpful feedback on both the technical content and grammar issues
• Kye and gmovchan for spotting a typo
• Hugh's email exchanges helped me significantly to improve the presentation of concepts and exercises
• Christopher Patti for reviewing the book, providing feedback and brightening the day with kind words
• Users 73tada, DrBobHope, nlomb and others for feedback in this reddit thread
• mdBook — for web version of the book
  • mdBook-pagetoc — for adding table of contents for each chapter
  • minify-html — for minifying html files

Special thanks to Al Sweigart. His Automate the Boring Stuff book was instrumental for me to get started with Python.

License

The book is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

The code snippets are licensed under MIT, see LICENSE file.