Python split string based on conditional

Question

I want to split strings using a comma delimiter if the comma is preceded by a certain regex. Consider the case where my strings are in the format: "(bunch of stuff that might have commas) FOO_REGEX, (other stuff that might have commas) FOO_REGEX, ..." and I want to split the string on commas, but only if they're preceded by FOO_REGEX: ["(bunch of stuff that might have commas) FOO_REGEX", "(other stuff that might have commas) FOO_REGEX", tc.].

As a concrete example, consider splitting the following string:

"hi, hello! $$asdf, I am foo, bar $$jkl, cool"

into this list of three strings:

["hi, hello! $$asdf", 
"I am foo, bar $$jkl", 
"cool"]

Is there any easy way to do this in python?

Avinash Raj · Accepted Answer · 2015-04-03 08:12:59Z

2

You could use re.findall instead of re.split.

>>> import re
>>> s = "hi, hello! $$asdf, I am foo, bar $$jkl, cool"
>>> [j for i in re.findall(r'(.*?\$\$[^,]*),\s*|(.+)', s) for j in i if j]
['hi, hello! $$asdf', 'I am foo, bar $$jkl', 'cool']

OR

Use external regex module to support variable length lookbehind since re won't support variable length look-behind assertions.

>>> import regex
>>> s = "hi, hello! $$asdf, I am foo, bar $$jkl, cool"
>>> regex.split(r'(?<=\$\$[^,]*),\s*', s)
['hi, hello! $$asdf', 'I am foo, bar $$jkl', 'cool']

edited Apr 3, 2015 at 8:12

answered Apr 3, 2015 at 8:07

Avinash Raj

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1 Comment

Halcyon Abraham Ramirez Over a year ago

Hope this gets added soon. Because the link you gave is awesome

Wiktor Stribiżew · Accepted Answer · 2015-04-03 08:14:28Z

1

You can use a positive look-behind if the FOO_REGEX is fixed-width. Here, you will get your line split after "$$asdf,"

See a sample working program:

import re    
str = 'hi, hello! $$asdf, I am foo, bar $$jkl, cool'
splts = re.split('(?<=\$\$asdf), *', str)
print splts

Output:

['hi, hello! $$asdf', 'I am foo, bar $$jkl, cool']

edited Apr 3, 2015 at 8:14

answered Apr 3, 2015 at 8:07

Wiktor Stribiżew

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