Split string by comma unless followed by a space or a '+'

Question

I'm trying to split an extremely long string by commas. I have two requirements, however:

the comma cannot be followed by a space
the comma cannot be followed by a '+' symbol

so for example, the input would be:

text = "hello,+how are you?,I am fine, thanks"

and the output of this is:

['hello,+how are you?', 'I am fine, thanks']

i.e. the only comma that seperated the values was the one that was not followed by a '+' or a space

I have managed requirement 1) as follows:

re.split(r',(?=[^\s]+)',text)

I cannot figure out how to add requirement 2)

this might be helpful https://stackoverflow.com/questions/31201690/find-word-not-followed-by-a-certain-character/31201710#31201710 — Uuuuuumm, Jul 24 '20 at 14:27
@mk no need to escape anything: `re.split(r',(?=[^\s+])',text)` == `['hello,+how are you?', 'I am fine, thanks']` — Patrick Artner, Jul 24 '20 at 14:27
`re.split(r',(?![+ ])', text)` <-- Negative lookahead. Matches anything containing `,` unless there is a `+` character or a space afterwards. — Hampus Larsson, Jul 24 '20 at 14:28
@Anthony, doesn't work, result is: `['hello,+how are you?', ' am fine, thanks']` — ipj, Jul 24 '20 at 14:35

score 3 · Answer 1 · answered Jul 24 '20 at 14:37

The simplest solution is to only look for the pattern that you don't want, and exclude it altogether. You do that using negative-lookahead in regular-expression.

>>> text = "hello,+how are you?,I am fine, thanks"
>>> re.split(r',(?![+ ])', text)
['hello,+how are you?', 'I am fine, thanks']

This will match , unless it's followed either by a literal + or a space.

score 0 · Answer 2 · answered Jul 24 '20 at 14:31

0

Try this

re.split(r',(?=[^\s +])',text)

answered Jul 24 '20 at 14:31

Pratyaksh Saini

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Why the space between `\s` and `+`? – mkrieger1 Jul 24 '20 at 14:31
i think space is like or here. its giving this output ['hello,+how are you?', 'I am fine, thanks'], isn't that correct? – Pratyaksh Saini Jul 24 '20 at 14:34
(\s +), i am saying this means, (whitespace or plus-sign), '\s'=whitespace, ' '=or, '+'=plus-sign – Pratyaksh Saini Jul 24 '20 at 15:02
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`' '` does not mean "or". All characters inside `[ ]` are already "or"ed. – mkrieger1 Jul 24 '20 at 15:39

score 0 · Answer 3 · answered Jul 24 '20 at 22:33

I suggest you go with @HampusLarsson's answer, but I'd like to squeeze in an answer that doesn't use imported modules:

s = "hello,+how are you?,I am fine, thanks"

ind = [0]+[i for i,v in enumerate(s)
           if v == ',' and s[i+1] not in [' ','+']]

parts = [s[i:j].lstrip(',')
         for i,j in zip(ind, ind[1:]+[None])]

print(parts)

Output:

['hello,+how are you?', 'I am fine, thanks']

Split string by comma unless followed by a space or a '+'

3 Answers3