Expanding Regex In Python

My program takes in a regex for describing a set of devices. For example, --device=dev{01,02}{nyc}.hukka.com should expand to dev01nyc.hukka.com and dev02nyc.hukka.com How can I

Solution 1:

If we re.split on the braces, we get:

In [7]: re.split(r'\{(.*?)\}',userstring)
Out[7]: ['--device=dev', '01,02', '', 'nyc', '.hukka.com']

Every other item in the list came from inside braces, which we next need to split on commas:

In [8]: [ part.split(',') if i%2else [part]  for i,part inenumerate(re.split(r'\{(.*?)\}',userstring)) ]
Out[8]: [['--device=dev'], ['01', '02'], [''], ['nyc'], ['.hukka.com']]

Now we can use itertools.product to enumerate the possibilities:

import re
import itertools

userstring = '--device=dev{01,02}{nyc}.hukka.com'for x in itertools.product(*[ part.split(',') if i%2else [part]  for i,part inenumerate(re.split(r'\{(.*?)\}',userstring)) ]):
    print(''.join(x))

yields

--device=dev01nyc.hukka.com
--device=dev02nyc.hukka.com

Solution 2:

Simply by extract the first braces to a group and iterate over this group :

import re

user_arg = "dev{01,02}{nyc}.hukka.com"

regex = re.compile('dev{(?P<dev_id>[^}]*)}{(nyc)}.hukka.com')
result = regex.search(user_arg)

devices = []
for dev_id in result.group(1).split(',') :
    devices.append("dev%s%s.hukka.com" % (dev_id, result.group(2)))

print devices

That returns :

$ ['dev01nyc.hukka.com', 'dev02nyc.hukka.com']