remove white space between specific characters using regex in python

Question

I am trying to use regex to remove white spaces in the sequence of consecutive '?' and/or '!' in a string. One example is that "what is that ?? ? ? ?? ??? ? ! ! ! ? !" should be changed to "what is that ??????????!!!?!". That is, I want to concatenate all '?' and '!' without space in between. My current code doesn't work out well:

import re
s = "what is that ?? ? ? ?? ??? ? ! ! ! ? !"
s = re.sub("\? +\?", "??", s)
s = re.sub("\? +\!", "?!", s)
s = re.sub("\! +\!", "!!", s)
s = re.sub("\! +\?", "!?", s)

which produces 'what is that ??? ???????!! !?!', where some spaces are obviously not deleted. what is going wrong in my code and how to revise it?

g.d.d.c · Accepted Answer · 2018-01-02 03:09:11Z

4

You're simply trying to condense whitespace around the punctuation, yeah? How about something like this:

>>> import re
>>> s = "what is that ?? ? ? ?? ??? ? ! ! ! ? !"
>>> 
>>> re.sub('\s*([!?])\s*', r'\1', s)
'what is that??????????!!!?!'

If you're really interested in why your approach isn't working, it has to do with how regular expressions move through a string. When you write re.sub("\? +\?", "??", s) and run it on your string, the engine works through like this:

s = "what is that ?? ? ? ?? ??? ? ! ! ! ? !"
# first match -----^^^
# internally, we have:
s = "what is that ??? ? ?? ??? ? ! ! ! ? !"
# restart scan here -^
# next match here ----^^^
# internally:
s = "what is that ??? ??? ??? ? ! ! ! ? !"
# restart scan here ---^
# next match here ------^^^

And so on. There are ways you can prevent the cursor from advancing as it's checking for a match (check out positive look-ahead).

edited Jan 2, 2018 at 3:09

answered Jan 2, 2018 at 2:59

g.d.d.c

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1 Comment

Daniele Over a year ago

This is one of the best solutions I could find. It has still a small issue for me which is that for This is! ? a test! ? it will return This is!?a test!? while I expect to have This is!? a test!? (keep the space between the question mark and the 'a'). Any further help would be very much appreciated

user9158931 · Accepted Answer · 2018-01-02 03:13:45Z

0

If you want as @g.d.d.c said and sentence pattern is same then then you can try this :

string_="what is that ?? ? ? ?? ??? ? ! ! ! ? !"
string_1=[]
symbols=[]
string_1.append(string_[:string_.index('?')])
symbols.append(string_[string_.index('?'):])
string_1.append("".join(symbols[0].split()))
print("".join(string_1))

output:

what is that ??????????!!!?!

answered Jan 2, 2018 at 3:13

user9158931

Comments

james-see · Accepted Answer · 2018-01-02 03:16:03Z

0

My approach involves splitting the string into two and then handling the problem area with regex (removing spaces) and then joining the pieces back together.

import re s = "what is that ?? ? ? ?? ??? ? ! ! ! ? !" splitted = s.split('that ') # don't forget to add back in 'that' later splitfirst = splitted[0] s = re.sub("\s+", "", splitted[1]) finalstring = splitfirst+'that '+s print(finalstring) output:

╭─jc@jc15 ~/.projects/tests ╰─$ python3 string-replace-question-marks.py what is that ??????????!!!?!

answered Jan 2, 2018 at 3:16

james-see

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