Regular expressions

Question

Keep in mind that this is my first time using regular expressions, so please dont judge.
I have a code:

import re
def solution(s, markers):
markers = "".join(markers)
return re.sub('#[^\n]+', '', s)
print(solution("a #b\nc\nd !e f g", ["#", "!"]))

I want the # in line 4 to be replaced with an unknown character, is there a way to do it? I tried just putting markers instead of # but that didnt work. I appreciate all the help

Answer 1

You can use f-strings (or even <string>.format() to interpolate the markers into the strings.

So for example, you can change the regex in line 4
from
'#[^\n]+'
to
f"{markers}[^\n]+" (note that the `f` has to be outside the string)

But because you want to choose from any one of the markers, enclose the markers in square brackets
f"[{markers}][^\n]+"

Answer 2

XXX okay, thank you very much

Answer 3

XXX thank you so much, that worked, if you have time can yo answer one more question. If I have a whitespace at the end of the line, before the new line, how do I remove it?

Answer 4

XXX the code prints :
a
b
c
but after "a" there is a white space.
how do I remove all the whitespaces that are only at the end of the line?

Answer 5

I haven't really worked much with regex myself. I just knew the solution to your problem. This is the thread I have started, follow it so you get notified when someone answers.

Answer 6

Kirill Vidov see this code
https://code.sololearn.com/c5ooiYKi4eXG/?ref=app

The same thing has been done as before, except now, I am passing the string returned by re.sub to another re.sub which is processing the processed string. In the outer re.sub, I have used the lookahead pattern to match all white spaces followed by a new line. See this link for lookahead operators
https://www.rexegg.com/regex-lookarounds.html

Answer 7

@XXX thank you very mmuch

Answer 8

I didn't really understand what you want. Can you explain with an example?

Answer 9

Hmm I don't really know how to do that. I tried doing this

import re
def solution(s, markers):
markers = "".join(markers)
return re.sub(r'\s\n', '', re.sub(rf'{markers}[^\n]+', '', s))
print(solution("a #b\nc\nd !e f g", ["#", "!"]))

But that removes the white space as well as the new line. I'll start a bew QnA thread and send you the link.