python regex comma separated group

Question

I have a string that I am trying to create a group of only the items that have commas. So far, I am able to create a group, what I'm trying to do is ensure that the string contains the word nodev. If the string doesn't contain that word, a match should show, otherwise, the regex should not match anything.

String:

"/dev/mapper/ex_s-l_home /home  ext4    rw,exec,auto,nouser,async    1  2"

Regex that matches the comma delimited group:

([\w,]+[,]+\w+)

I've tried this regex but with no luck:

(?!.*nodev)([\w,]+[,]+\w+)

I'm using https://pythex.org/ and am expecting my output to have one match that contains "rw,exec,auto,nouser,async". This way I plan on appending ,nodev to the end of the string if it doesn't contain it.

Looking for a regex only solution(no functions)

I'm using pythex.org and am expecting my output to have one match that contains "rw,exec,auto,nouser,async" — Brian Putt
– Brian Putt, Commented Sep 23, 2014 at 13:49

falsetru · Accepted Answer · 2014-09-23 14:33:43Z

2

>>> import re
>>> s = "/dev/mapper/ex_s-l_home /home  ext4    rw,exec,auto,nouser,async    1  2"
>>> s2 = "/dev/mapper/ex_s-l_home /home  ext4    rw,exec,auto,nodev,nouser,async    1  2"
>>> re.findall(r'(?<=\s)(?!.*nodev)(?=\S*,\S*)\S+', s)
['rw,exec,auto,nouser,async']
>>> re.findall(r'(?<=\s)(?!.*nodev)(?=\S*,\S*)\S+', s2)
[]

To append ,nodev:

>>> re.sub(r'(?<=\s)(?!.*nodev)(?=\S*,\S*)\S+', r'\g<0>,nodev', s)
'/dev/mapper/ex_s-l_home /home  ext4    rw,exec,auto,nouser,async,nodev    1  2'
>>> re.sub(r'(?<=\s)(?!.*nodev)(?=\S*,\S*)\S+', r'\g<0>,nodev', s2)
'/dev/mapper/ex_s-l_home /home  ext4    rw,exec,auto,nodev,nouser,async    1  2'

pythex demo

edited Sep 23, 2014 at 14:33

answered Sep 23, 2014 at 13:56

falsetru

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2 Comments

Avinash Raj Over a year ago

i think it won't work if both comma seperated values are present within a single string variable.

falsetru Over a year ago

@AvinashRaj, I think the string came from fstab. So it will have one options field (rw,exec,auto,nouser,async) per line.

Avinash Raj · Accepted Answer · 2014-09-23 14:19:01Z

0

Complete regex solution.

For this to work, you need to import regex module.

>>> import regex
>>> s = " /dev/mapper/ex_s-l_home /home  ext4 rw,exec,auto,nouser,async    1  2 rw,exec,nodev,nouser,async    1  2 nodevfoo bar"
>>> m = regex.findall(r'(?<=^|\s)\b(?:(?!nodev)\w+(?:,(?:(?!nodev)\w)+)+)+\b(?=\s|$)', s)
>>> m
['rw,exec,auto,nouser,async']

answered Sep 23, 2014 at 14:19

Avinash Raj

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