How to specify long url patterns using Regex so that they follow PEP8 guidelines

Question

I have a long url pattern in Django similar to this:

url(r'^(?i)top-dir/(?P<first_slug>[-\w]+?)/(?P<second_slug>[-\w]+?)/(?P<third_slug>[-\w]+?).html/$',
    'apps.Discussion.views.pricing',

Definitely it doesn't follow PEP8 guide as the characters are more than 80 in a single line. I have found two approach of solving this:

The first one (using backslash):

   url(r'^(?i)top-dir/(?P<first_slug>[-\w]+?)/(?P<second_slug>[-\w]+?)'\
       '/(?P<third_slug>[-\w]+?).html/$',
       'apps.Discussion.views.pricing',

The second one - using ():

 url((r'^(?i)top-dir/(?P<first_slug>[-\w]+?)/(?P<second_slug>[-\w]+?)',
      r'/(?P<third_slug>[-\w]+?).html/$'),
      'apps.Discussion.views.pricing'),  

Both of them break by Regex. Is there a better approach to solve this issue. OR Is it a bad practice to write such long Regex for urls.

Answer 1

Adjacent strings are concatenated, so you can do something like this:

url(r'^(?i)top-dir/(?P<first_slug>[-\w]+?)/'
    r'(?P<second_slug>[-\w]+?)/'
    r'(?P<third_slug>[-\w]+?).html/$',
    'apps.Discussion.views.pricing',)

Answer 2

PEP8 has no regex formatting tips. But try these:

• use re.compile and have these benefits
  • quicker to match/search on them
  • reference them under a (short) name!
• write the regex multiline with (white)spaces
  • use re.VERBOSE to ignore whitespace in the regex string
  • use flags instead of “magic groups” ((?i) → re.IGNORECASE)

 

slugs = re.compile(r'''
    ^
    top-dir/
    (?P<first_slug>[-\w]+?)/
    (?P<second_slug>[-\w]+?)/
    (?P<third_slug>[-\w]+?).html/
    $
        ''', re.VERBOSE|re.IGNORECASE)

url(slugs, 'apps.Discussion.views.pricing', ...)