I define a split function as lambda x: re.split('[(|)|.]', x), and when I applied this function to my original strings, it always generates some empty strings. For example:
When applied to string:
(Type).(Terrorist organization)AND(Involved in attacks).(nine-eleven)
The result is:
['', 'Type', '', '', 'Terrorist organization', 'AND', 'Involved in attacks', '', '', 'nine-eleven', '']
I know I can simply remove those empty strings manually, but is there any smart way to get rid of them?
grab as many separators as you can with + instead of only one:
re.split('[().]+', s)
unfortunately, this doesn't suffice as re.split notoriously yields empty strings at start & end of the string:
['', 'Type', 'Terrorist organization', 'AND', 'Involved in attacks', 'nine-eleven', '']
but you can filter them out by using post processing:
[x for x in re.split('[().]+', s) if x]
On the other hand, you could revert the regex and use re.findall to match as much non-separators as possible:
re.findall('[^().]+', s)
this directly yields:
['Type', 'Terrorist organization', 'AND', 'Involved in attacks', 'nine-eleven']
The regexp matches ), ., and ( individually. Since these are next to each other in the input, there's an empty string between them, so the result contains those empty strings.
If you want to treat a sequence of delimiters as a single delimiter, add a + quantifier to the regexp so it matches them as a sequence.
re.split('[|().]+', x)
The empty string at the beginning is because of the empty string before the first (. Similarly, the empty string at the end is from the empty string in the input after the last ). I don't think there's a simple way to prevent these, just remove them from the result.
You can filter:
filter(lambda x: x, re.split('[().]+', s))
Test:
import re
s = '(Type).(Terrorist organization)AND(Involved in attacks).(nine-eleven)'
print(list(filter(None, re.split('[().]+', s))))
Result:
['Type', 'Terrorist organization', 'AND', 'Involved in attacks', 'nine-eleven']
filter(lambda x: x, is slightly redundant. You can write filter(None,
|multiple times in the[]character set?[..]means match any character inside. You can’t use capture groups inside them.[().]will match the literal characters present.(,|,),.) inside the square brackets is considered a separate delimiter.