Split string with multiple delimiters in Python


I found some answers online, but I have no experience with regular expressions, which I believe is what is needed here.

I have a string that needs to be split by either a ‘;’ or ‘, ‘
That is, it has to be either a semicolon or a comma followed by a space. Individual commas without trailing spaces should be left untouched

Example string:

"b-staged divinylsiloxane-bis-benzocyclobutene [124221-30-3], mesitylene [000108-67-8]; polymerized 1,2-dihydro-2,2,4- trimethyl quinoline [026780-96-1]"

should be split into a list containing the following:

('b-staged divinylsiloxane-bis-benzocyclobutene [124221-30-3]' , 'mesitylene [000108-67-8]', 'polymerized 1,2-dihydro-2,2,4- trimethyl quinoline [026780-96-1]') 
Asked By: gt565k



Do a str.replace('; ', ', ') and then a str.split(', ')

Answered By: Joe

This is how the regex look like:

import re
# "semicolon or (a comma followed by a space)"
pattern = re.compile(r";|, ")

# "(semicolon or a comma) followed by a space"
pattern = re.compile(r"[;,] ")

print pattern.split(text)
Answered By: Jochen Ritzel

Luckily, Python has this built-in 🙂

import re
re.split('; |, ', string_to_split)

Following your comment:

>>> a='Beautiful, is; better*thannugly'
>>> import re
>>> re.split('; |, |*|n',a)
['Beautiful', 'is', 'better', 'than', 'ugly']
Answered By: Jonathan Livni

Here’s a safe way for any iterable of delimiters, using regular expressions:

>>> import re
>>> delimiters = "a", "...", "(c)"
>>> example = "stackoverflow (c) is awesome... isn't it?"
>>> regex_pattern = '|'.join(map(re.escape, delimiters))
>>> regex_pattern
>>> re.split(regex_pattern, example)
['st', 'ckoverflow ', ' is ', 'wesome', " isn't it?"]

re.escape allows to build the pattern automatically and have the delimiters escaped nicely.

Here’s this solution as a function for your copy-pasting pleasure:

def split(delimiters, string, maxsplit=0):
    import re
    regex_pattern = '|'.join(map(re.escape, delimiters))
    return re.split(regex_pattern, string, maxsplit)

If you’re going to split often using the same delimiters, compile your regular expression beforehand like described and use RegexObject.split.

If you’d like to leave the original delimiters in the string, you can change the regex to use a lookbehind assertion instead:

>>> import re
>>> delimiters = "a", "...", "(c)"
>>> example = "stackoverflow (c) is awesome... isn't it?"
>>> regex_pattern = '|'.join('(?<={})'.format(re.escape(delim)) for delim in delimiters)
>>> regex_pattern
>>> re.split(regex_pattern, example)
['sta', 'ckoverflow (c)', ' is a', 'wesome...', " isn't it?"]

(replace ?<= with ?= to attach the delimiters to the righthand side, instead of left)

Answered By: Kos

In response to Jonathan’s answer above, this only seems to work for certain delimiters. For example:

>>> a='Beautiful, is; better*thannugly'
>>> import re
>>> re.split('; |, |*|n',a)
['Beautiful', 'is', 'better', 'than', 'ugly']

>>> b='1999-05-03 10:37:00'
>>> re.split('- :', b)
['1999-05-03 10:37:00']

By putting the delimiters in square brackets it seems to work more effectively.

>>> re.split('[- :]', b)
['1999', '05', '03', '10', '37', '00']
Answered By: Paul
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