Regular expression to match an empty string?

Question

I want to match and group any of these listed words:

aboutus/,race/,cruise/,westerlies/,weather/,reach/,gear/ or empty_string

Here is a solution, but which will not match the empty_string:

^(aboutus|race|cruise|westerlies|weather|reach|gear)/$

So my question is: How to include Empty string in this matching?

I still don't get a good solution for this.

So I added one more regex specially for empty_string:ie ^$.

Note: these regular expression is for django urls.py.

update: It will be better if the capturing group does not contain /

Answer 1

Use this

^$|^(aboutus|race|cruise|westerlies|weather|reach|gear)/$

Answer 2

try this:

^(aboutus|race|cruise|westerlies|weather|reach|gear)?/$

edit: if '/' is in every case except the empty string try this

^((aboutus|race|cruise|westerlies|weather|reach|gear)(/))?$

Answer 3

You can make the capturing group optional:

^(aboutus|race|cruise|westerlies|weather|reach|gear)?/$

Answer 4

import re

rgx = re.compile('^((aboutus|race|cruise|westerlies'
                 '|weather|reach|gear)/|)$')

# or

li = ['aboutus','race','cruise','westerlies',
      'weather','reach','gear']
rgx = re.compile('^((%s)/|)$' % '|'.join(li))


for s  in ('aboutus/',
           'westerlies/',
           'westerlies/ ',
           ''):
    m = rgx.search(s)
    print '%-21r%r' % (s,rgx.search(s).group() if m else m)  

result

'aboutus/'           'aboutus/'
'westerlies/'        'westerlies/'
'westerlies/ '       None
''                   ''