Strip whitespaces after and before of a specific list of punctuation symbols

Although I found some references in StackOverflow, I am unable to write the correct regular expression to achieve my goal. I want to remove whitespaces before and after of specific punctuation symbols from a string in python.

I have a function as follows.

def modify_answers(answers):
hyp =
for ans in answers:
# remove whitespace before - / ? . ! ;
newhyp = re.sub(r's([-/?.!,;](?:s|$))', r'1', ans)
# remove whitespace after - / $ _
newhyp = re.sub(r'', r'1', newhyp)
hyp.append(newhyp)
return hyp


Some examples of what I want to achieve:

"Tax pin number is 1 - 866 - 704 - 7388 ." ---> "Tax pin number is 1-866-704-7388."

"No , emu is not protected in Victoria ." ---> "No, emu is not protected in Victoria."

"Find is to lose as construct is to _ _ _ _ _ _ ." ---> "Find is to lose as construct is to ______."

"$ 1,0 is equal to $ 1,0 ." ---> "$1,0 is equal to $1,0."

Any help would be appreciated.

3 Answers
3

First, define a function that performs replacement:

import re

def replace(x):
y, z = x.groups()
if z in '-/?.!,;':
y = y.lstrip()
if z in '-/$_':
y = y.rstrip()
return y


The function takes a match pattern and performs replacement accordingly.

Now, define your pattern. You can pre-compile for efficiency.

p = re.compile(r'(s*([-/?.,!$_])s*)')


Call the compiled regex sub on each string with the callback defined earlier:

sub

cases = [
"Tax pin number is 1 - 866 - 704 - 7388 .",
"No , emu is not protected in Victoria .",
"Find is to lose as construct is to _ _ _ _ _ _ .",
"$ 1,0 is equal to $ 1,0 ."]

repl = [p.sub(replace, c) for c in cases]


print (repl)
['Tax pin number is 1-866-704-7388.', 'No, emu is not protected in Victoria.',
'Find is to lose as construct is to ______.', '$1,0 is equal to $1,0.']


re.compile()

You can do it like this:

import re

sentences = ["Tax pin number is 1 - 866 - 704 - 7388 .",
"No , emu is not protected in Victoria .",
"Find is to lose as construct is to _ _ _ _ _ _ .",
"$ 1,0 is equal to $ 1,0 ."]


def modify_answers(answers):
hyp =
for ans in answers:
# remove whitespace before - / ? . ! ;
new_hyp = re.sub(r's([/?.!;_-])(s|$)', r'1', ans)
new_hyp = re.sub(r's(,)(s|$)', r'1 ', new_hyp)
new_hyp = re.sub(r'(^|s)($)(s|$)', r' 2', new_hyp)
hyp.append(new_hyp.strip())
return hyp

for sentence in modify_answers(sentences):
print(sentence)


Output

Tax pin number is 1-866-704-7388.
No, emu is not protected in Victoria.
Find is to lose as construct is to______.
$1,0 is equal to $1,0.


Notes

/?.!;_-

-

,

,

$

$

Replace the pattern r' (?=[-/?.!])|(?<=[-/$_]) ' with empty string using re.sub

r' (?=[-/?.!])|(?<=[-/$_]) '

re.sub

>>> lst = ["Tax pin number is 1 - 866 - 704 - 7388 .",
... "No , emu is not protected in Victoria .",
... "Find is to lose as construct is to _ _ _ _ _ _ .",
... "$ 1,0 is equal to $ 1,0 ."]
>>>
>>> def modify_answers(answers):
... ptrn = re.compile(r' (?=[-/?.!])|(?<=[-/$_]) ')
... return [ptrn.sub('', answer) for answer in answers]
...
>>>
>>> pprint(modify_answers(lst))
['Tax pin number is 1-866-704-7388.',
'No , emu is not protected in Victoria.',
'Find is to lose as construct is to ______.',
'$1,0 is equal to $1,0.']


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