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I have the following strings

s1 = 'XXX-2 I LOVE : XXX XXX'
s2 = 'FOOD : XXX'
s3 = 'XXX-FOOD : XXX

I would like the following

s1 = '2 I LOVE'
s2 = 'FOOD'
s3 = 'FOOD'

s2 only has 1 delimiter : while s1 & s3 have 2 - & :

I would like to keep everything between the two delimiters - & : so I use the following \-(.*?)\: however I don't get s2

If I use the following \w+\-?(.*?)\: I get everything before -

I am terrible at regex, if someone could help me with this one and provide a link to understanding regex I would really appreciate it.

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4
  • s2 doesn't have two delimiters to use? Commented Jun 21, 2018 at 23:20
  • exactly why I am stuck Commented Jun 21, 2018 at 23:20
  • s2 doesn't meet your description of the original regex, so it's not clear what you want your regex to save. Additional explanations and/or examples are necessary. Commented Jun 21, 2018 at 23:22
  • perhaps the changes help Commented Jun 21, 2018 at 23:25

3 Answers 3

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The regex you need is: (?:\w+-)?(.*?):

(?:\w+-)? says to check for an initial sequence of word-like characters \w followed by a hyphen. Since we have that in parantheses, the question mark after it says this entire part is optional - i.e., either there will be \w+ and - at the beginning of the line, or neither of them will be there. The ?: part is just to tell Python that you're using the parantheses () here just for grouping, not because you want the matching parts to be captured and stored.

(.*?) - This matches the parts we actually want, and stores that in the capture group number 1. So if you have m = re.match(r"(?:\w+-)?(.*?):", 'XXX-2 I LOVE : XXX XXX'), then m.group(1) will contain 2 I LOVE.

(Note that neither - nor : need a backslash escape in regex in general (- needs quoting just inside [] character classes), so you can just write them out without escaping them.)

You might find tools like RegExr useful for exploring and understanding regexes.

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1

The following regex should work for your example

(?:[^-]+-)?([^:]+):.*
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5 Comments

how dude just how??? Thank you so much. Is this just from experience or do you mind sharing a good resource.
You're most welcome, regex looks scary at the beginning, but it gets easy when you get used to it. I just wrote that, but a good tool to test your regex is regex101.com
thank you thank you thank you!!! It looks so confusing at first but I want to get much better at it.
Just a note, @Sundar answer has more explanation on regex, and using \w+ instead of [^-]+ will work for your example, but will not work if you have a non-alphabet character befor the -
yes I was playing around with the link you provided me and ran into that problem.
1

We are using strip to remove the trailing space.

s1 = re.sub(r'[^a-zA-Z0-9\s]+|X','',s1).strip()
s2 = re.sub(r'[^a-zA-Z0-9\s]+|X','',s2).strip()
s3 = re.sub(r'[^a-zA-Z0-9\s]+|X','',s3).strip()

2 I LOVE
FOOD
FOOD
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1 Comment

I was going to resort to this since I was losing hope thank you!

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