Im trying to extract the text on the left, outside the parenthesis ():

import re
clean_title = re.match(r'(.*)\(.*\)', title.lower()) 
if clean_title:
   return clean_title.group(1).rstrip()

Any suggestions to improve it, maybe without regex?

Expected results:

>>'Alone in the Dark (The Cincinnati Series Book 2)'
>>'alone in the dark'
  • 3
    \$\begingroup\$ How certain are you that the parentheses will either occur in a pair at the end of the title, or not at all? Is there any chance of nested parentheses? How should it behave in such unexpected situations? \$\endgroup\$ – 200_success Aug 18 '17 at 6:23

You can use split() to split the whole text based on the first occurrence of the ( character. This will return a list, pick the first element of the list:

>>> text = 'Alone in the Dark (The Cincinnati Series Book 2)'
>>> text.split('(')[0]
'Alone in the Dark '

Assuming the text on the left cannot contain opening parenthesis, splitting by the first opening parenthesis might work as well:

>>> clean_title = 'Alone in the Dark (The Cincinnati Series Book 2)'
>>> clean_title.split('(', 1)[0].lower().rstrip()
'alone in the dark'

Note that it will not fail even if there are no parenthesis:

>>> clean_title = 'Test'
>>> clean_title.split('(', 1)[0].lower().rstrip()

As far as the regular expression approach, you might also use re.sub() which would not require checking if there is a match or not. And, as a bonus, let's account for the extra space before the parenthesis:

>>> re.sub(r"(.*?)\s?\(.*?\)", r"\1", clean_title).lower()
'alone in the dark'


>>> re.sub(r"\s?\(.*?\)", r"", clean_title).lower()
'alone in the dark'

You can also do the lowering part in a replacement function:

>>> re.sub(r"(.*?)\s?\(.*?\)", lambda m: m.group(1).lower(), clean_title)
'alone in the dark'

Also note that I'm using non-greedy regular expressions.

  • 1
    \$\begingroup\$ r"(.*?)\s?\(.*?\)", r"\1" seems overkill if not using the lambda - r"\s*\(.*\)", "" (replacing with nothing) should be enough, right? \$\endgroup\$ – muru Aug 18 '17 at 6:37
  • \$\begingroup\$ @muru good point, included into the answer, thanks! \$\endgroup\$ – alecxe Aug 18 '17 at 13:42

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