Splitting by “,” in python

Question

I am trying to split a string by commas ","

For example:

"hi, welcome"  I would like to produce ["hi","welcome"]

however:

"'hi,hi',hi" I would like to produce ["'hi,hi'","hi"]

"'hi, hello,yes','hello, yes','eat,hello'" I would like to produce ["'hi, hello,yes'","'hello, yes'","'eat,hello'"]

"'hiello, 332',9" I would like to produce ["'hiello, 332'","9"]

I dont think the .split() function could be used, Does anyone know a way I could do this, perhaps with regex?

Answer 1

You can use the csv module with the quotechar argument, or you can convert your inputs to use the more standard " character for their quote character.

>>> import csv
>>> from cStringIO import StringIO
>>> first=StringIO('hi, welcome')
>>> second=StringIO("'hi,hi',hi")
>>> third=StringIO("'hi, hello,yes','hello, yes','eat,hello'")
>>> fourth=StringIO("'hiello, 332',9")
>>> rfirst=csv.reader(first,quotechar="'")
>>> rfirst.next()
['hi', ' welcome']
>>> rsecond=csv.reader(second,quotechar="'")
>>> rsecond.next()
['hi,hi', 'hi']
>>> rthird=csv.reader(third,quotechar="'")
>>> rthird.next()
['hi, hello,yes', 'hello, yes', 'eat,hello']
>>> rfourth=csv.reader(fourth,quotechar="'")
>>> rfourth.next()
['hiello, 332', '9']

>>> second=StringIO('"hi,hi",hi') # This will be more straightforward to interpret.
>>> r=csv.reader(second)
>>> r.next()
['hi,hi', 'hi']
>>> third=StringIO('"hi, hello,yes","hello, yes","eat,hello"')
>>> r=csv.reader(third)
>>> r.next()
['hi, hello,yes', 'hello, yes', 'eat,hello']

Answer 2

With regex, as you asked for:

import re

>>>pattern = re.compile(r"([^',]+,?|'[^']+,?')")
>>>re.findall(pattern, "hi, welcome")
['hi', 'welcome']

>>>re.findall(pattern, "'hi, hello,yes','hello, yes','eat,hello'")
["'hi, hello,yes'", "'hello, yes'", "'eat,hello'"]

>>>re.findall(pattern, "'hi,hi',hi")
 ["'hi,hi'", 'hi']

>>>re.findall(pattern, "'hiello, 332',9")
["'hiello, 332'", '9']

The first part of the pattern, [^',]+,? , catches segments without quotes and without commas. It might have a comma at the end or it might not (if it's the last segment).

The second part, '[^']+,?' , catches segments that are enclosed by quotes. It should not have more quotes internally, but it may have commas.

Answer 3

you could use a csv reader with , as delimiter and ' as quotechar. that seems to be compatible with what you expect.

Answer 4

Doing this directly without csv or re isn't that problematic:

def splitstring(s):
    result = []
    for i, piece in enumerate(s.split("'")):
        if piece:
            if i % 2:  # odd pieces are between quotes
                result.append("'" + piece + "'")
            else:  # even pieces aren't
                for subpiece in piece.split(","):
                    if subpiece:
                        result.append(subpiece)
    return result