Function re.split

Function split works similary to split method in strings, but in re.split function you can use regular expressions which means dividing a string into parts using more complex conditions.

For example, ospf_route string should be split by spaces (as in str.split method):

In [1]: ospf_route = 'O     10.0.24.0/24 [110/41] via 10.0.13.3, 3d18h, FastEthernet0/0'

In [2]: re.split(r' +', ospf_route)
Out[2]:
['O',
 '10.0.24.0/24',
 '[110/41]',
 'via',
 '10.0.13.3,',
 '3d18h,',
 'FastEthernet0/0']

Similarly, commas can be removed:

In [3]: re.split(r'[ ,]+', ospf_route)
Out[3]:
['O',
 '10.0.24.0/24',
 '[110/41]',
 'via',
 '10.0.13.3',
 '3d18h',
 'FastEthernet0/0']

And if necessary, get rid of square brackets:

In [4]: re.split(r'[ ,\[\]]+', ospf_route)
Out[4]: ['O', '10.0.24.0/24', '110/41', 'via', '10.0.13.3', '3d18h', 'FastEthernet0/0']

Function split has a peculiarity of working with groups (expressions in parentheses). If you specify the same expression with parentheses, the resulting list will include separators.

For example, word via is specified as a separator:

In [5]: re.split(r'(via|[ ,\[\]])+', ospf_route)
Out[5]:
['O',
 ' ',
 '10.0.24.0/24',
 '[',
 '110/41',
 ' ',
 '10.0.13.3',
 ' ',
 '3d18h',
 ' ',
 'FastEthernet0/0']

To disable such behavior you should make a noncapture group. That is, disable capturing of group elements:

In [6]: re.split(r'(?:via|[ ,\[\]])+', ospf_route)
Out[6]: ['O', '10.0.24.0/24', '110/41', '10.0.13.3', '3d18h', 'FastEthernet0/0']