Replace multiple matching groups with modified captured gropus

I am reading text from a file that contains flags start and end. I want to replace everything between start and end with the same text except I want to remove any newlines in the matching group.

I tried to do it as follows:

import re
start = '---'
end = '==='
text = '''\
Some text
---line 1
line 2 
line 3===
More text
...
Some more text
---line 4
line 5===
and even more text\
'''
modified = re.sub(pattern=rf'{start}(.+){end}', repl=re.sub(r'\n', ' ', r'\1'), string=text, flags=re.DOTALL)
print(modified)

This prints:

Some text
line 1
line 2 
line 3===
More text
...
Some more text
---line 4
line 5
and even more text

Couple of issues with this, 1. it matches the biggest group (and not the smaller matching groups), and 2. it does not remove the newlines.

I am expecting the output to be:

Some text
line 1 line 2 line 3
More text
...
Some more text
line 4 line 5
and even more text

Any help will be appreciated. Thank you!

>Solution :

Use non-greedy modifier (?) in the capturing group. Also, change the replacement function for simple str.replace:

import re

start = "---"
end = "==="

text = """\
Some text
---line 1
line 2
line 3===
More text
...
Some more text
---line 4
line 5===
and even more text\
"""

modified = re.sub(
    pattern=rf"{start}(.+?){end}",
    repl=lambda g: g.group(1).replace("\n", " "),
    string=text,
    flags=re.DOTALL,
)
print(modified)

Prints:

Some text
line 1 line 2 line 3
More text
...
Some more text
line 4 line 5
and even more text