Remove all chapters and corresponding titles in .txt file in python

I am working on a book in .txt format in python.

I would like to remove all chapters and corresponding titles. All of them are introduced by means of the word, CHAPTER, as in the example below:

\n\n\n\nCHAPTER 2. I OBSERVE\n\n\n

All have four \n\n\n\n before the UPPERCASE word CHAPTER, but after the chapter title, the numbers of \ n vary. So the condition I would like to impose is: Whenever \n\n\n\nCHAPTER is found, it deletes the text up to and including the next \ n.

\n\n\n\nCHAPTER 2. I OBSERVE\n\n\n -----> \n\n

Solution

Try this:

import re

with open('book.txt', 'r') as f:
    text = ''.join(f.readlines())

text = re.sub(r'\n{4}CHAPTER.*\n+', '\n\n', text)

with open('book.txt', 'w') as f:
    f.write(text)

It matches all sequences of:

4 newlines (\n{4})
the text "CHAPTER"
followed by some title text (.*)
and any amount of newlines thereafter (\n+)

and replaces them with two newlines (\n\n).

Note: this code overwrites the original file with the modifications. You may want to write to a different file & keep the original for different analysis. Otherwise, you can just directly pass the data to your NLP library.