用逗号分割字符串，忽略字符串内的逗号。 正在尝试CSV

Question

I have a string like this:

s = '1,2,"hello, there"'

And I want to turn it into a list:

[1,2,"hello, there"]

Normally I'd use split:

my_list = s.split(",") 

However, that doesn't work if there's a comma in a string.

So, I've read that I need to use cvs, but I don't really see how. I've tried:

from csv import reader
s = '1,2,"hello, there"'
ll = reader(s)
print ll 
for row in ll:
    print row

Which writes:

<_csv.reader object at 0x020EBC70>

['1']
['', '']
['2']
['', '']
['hello, there']

I've also tried with

ll = reader(s, delimiter=',')

Answer 1

It is that way because you provide the csv reader input as a string. If you do not want to use a file or a StringIO object just wrap your string in a list as shown below.

>>> import csv
>>> s = ['1,2,"hello, there"']
>>> ll = csv.reader(s, delimiter=',', quotechar='"', quoting=csv.QUOTE_MINIMAL)
>>> list(ll)
[['1', '2', 'hello, there']]

Answer 2

It sounds like you probably want to use the csv module. To use the reader on a string, you want a StringIO object.

As an example:

>> import csv, StringIO
>> print list(csv.reader(StringIO.StringIO(s)))
[['1', '2', 'hello, there']]

To clarify, csv.reader expects a buffer object, not a string. So StringIO does the trick. However, if you're reading this csv from a file object, (a typical use case) you can just as easily give the file object to the reader and it'll work the same way.

Answer 3

It's usually easier to re-use than to invent a bicycle... You just to use csv library properly. If you can't for some reason, you can always check the source code out and learn how's the parsing done there.

Example for parsing a single string into a list. Notice that the string in wrapped in list.

>>> import csv
>>> s = '1,2,"hello, there"'
>>> list(csv.reader([s]))[0]
['1', '2', 'hello, there']

Answer 4

You can split first by the string delimiters, then by the commas for every even index (The ones not in the string)

import itertools

new_data = s.split('"')
for i in range(len(new_data)):
    if i % 2 == 1: # Skip odd indices, making them arrays
       new_data[i] = [new_data[i]]
    else:
        new_data[i] = new_data[i].split(",")
data = itertools.chain(*new_data)

Which goes something like:

'1,2,"hello, there"'
['1,2,', 'hello, there']
[['1', '2'], ['hello, there']]
['1', '2', 'hello, there']

But it's probably better to use the csv library if that's what you're working with.

Answer 5

You could also use ast.literal_eval if you want to preserve the integers:

>>> from ast import literal_eval
>>> literal_eval('[{}]'.format('1,2,"hello, there"'))
[1, 2, 'hello, there']