Getting a line in a large file's content

Question

I am wondering how to implement Aaron Digulla's answer in this question: Fastest Text search method in a large text file

with open ('test.txt', 'rt') as myfile:
    contents = myfile.read() 
    match = re.search("abc", contents)

What's next, so that I can find the previous EOL and next EOL, and so that I can extract the line?

Answer 1

Replace

match = re.search("abc", contents)

with

match = re.search("^.*abc.*$", contents, re.M)

It will match the whole line containing "abc". Used with re.M flag ^ matches the beginning of a line and $ its end.

Here is an example:

import re

s = """
Twinkle, twinkle
Little star!
How I wonder 
What you are!
"""

term = "star"
match = re.search(f"^.*{term}.*$", s, re.M)
print(match.group(0))

It gives:

Little star!