python - How to split by commas that are not within parentheses?

Question

Say I have a string like this, where items are separated by commas but there may also be commas within items that have parenthesized content:

(EDIT: Sorry, forgot to mention that some items may not have parenthesized content)

"Water, Titanium Dioxide (CI 77897), Black 2 (CI 77266), Iron Oxides (CI 77491, 77492, 77499), Ultramarines (CI 77007)"

How can I split the string by only those commas that are NOT within parentheses? i.e:

["Water", "Titanium Dioxide (CI 77897)", "Black 2 (CI 77266)", "Iron Oxides (CI 77491, 77492, 77499)", "Ultramarines (CI 77007)"]

I think I'd have to use a regex, perhaps something like this:

([(]?)(.*?)([)]?)(,|$)

but I'm still trying to make it work.

Answer 1

Use a negative lookahead to match all the commas which are not inside the parenthesis. Splitting the input string according to the matched commas will give you the desired output.

,s*(?![^()]*))

DEMO

>>> import re
>>> s = "Water, Titanium Dioxide (CI 77897), Black 2 (CI 77266), Iron Oxides (CI 77491, 77492, 77499), Ultramarines (CI 77007)"
>>> re.split(r',s*(?![^()]*))', s)
['Water', 'Titanium Dioxide (CI 77897)', 'Black 2 (CI 77266)', 'Iron Oxides (CI 77491, 77492, 77499)', 'Ultramarines (CI 77007)']