python: padding punctuation with white spaces (keeping punctuation)

Question

What is an efficient way to pad punctuation with whitespace?

input:

s = 'bla. bla? bla.bla! bla...'

desired output:

 s = 'bla . bla ? bla . bla ! bla . . .'

Comments:

1. I don't care how many whitespaces are there between tokens. (but they'll need to be collapsed eventually)
2. I don't want to pad all punctuation. Say I'm interested only in .,!?().

Answer 1

You can use a regular expression to match the punctuation characters you are interested and surround them by spaces, then use a second step to collapse multiple spaces anywhere in the document:

s = 'bla. bla? bla.bla! bla...'
import re
s = re.sub('([.,!?()])', r' \1 ', s)
s = re.sub('\s{2,}', ' ', s)
print(s)

Result:

bla . bla ? bla . bla ! bla . . .

Answer 2

If you use python3, use the maketrans() function.

import string   
text = text.translate(str.maketrans({key: " {0} ".format(key) for key in string.punctuation}))