Parse a single CSV string?

Question

Is there a way that I can parse a single comma delimited string without using anything fancy like a csv.reader(..) ? I can use the split(',') function but that doesn't work when a valid column value contains a comma itself. The csv library has readers for parsing CSV files which correctly handle the aforementioned special case, but I can't use those because I need to parse just a single string. However if the Python CSV allows parsing a single string itself then that's news to me.

Solution 1

Take a closer look at the documentation for the csv module, which says:

reader(...)
    csv_reader = reader(iterable [, dialect='excel']
                            [optional keyword args])
        for row in csv_reader:
            process(row)

    The "iterable" argument can be any object that returns a line
    of input for each iteration, such as a file object or a list.  The
    optional "dialect" parameter is discussed below.  The function
    also accepts optional keyword arguments which override settings
    provided by the dialect.

So if you have string:

>>> s = '"this is", "a test", "of the csv", "parser"'

And you want "an object that returns a line of input for each iteration", you can just wrap your string in a list:

>>> r = csv.reader([s])
>>> list(r)
[['this is', 'a test', 'of the csv parser']]

And that's how you parse a string with the csv module.

Solution 2

You can still parse a single string with csv. Use StringIO to write a string buffer (also known as memory files):

import csv
from StringIO import StringIO

s = "your string"
buff = StringIO(s)

reader = csv.reader(buff)
for line in reader:
    print(line)

Solution 3

>>> import csv
>>> s = '"Yes, this line",can be, parsed as csv'
>>> list(csv.reader([s]))[0]
['Yes, this line', 'can be', ' parsed as csv']
>>>

Basically just @larsks answer above but more brief and demonstrating that it works on csv values that have commas inside quotes.

If you upvote me, upvote the other answer too. https://stackoverflow.com/a/35822856/1196339

Solution 4

String to Pandas DataFrame:

import pandas as pd
from io import StringIO

csv_str="Column1,Column2\n1,2\n3,4"

buff = StringIO(csv_str)
df = pd.read_csv(buff)

DataFrame:

Out[1]: 
   Column1  Column2
         1        2
         3        4

For other delimiters add something like delimiter="\t" to read_csv().

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Comments

[rafaelc]

I guess it would be more elegant to use iter(s) as to a general iterator instead of [s] (specifying a list). But you have my +1

[swooby]

This probably won't work if the string has quoted linefeeds inside of the values; @alecxe's answer makes more sense

[Christian Groleau]

For Python 3 use from io import StringIO see here

[Elias Strehle]

But be careful with non-ASCII strings! 'If [Unicode and 8-bit strings] are used, 8-bit strings that cannot be interpreted as 7-bit ASCII (that use the 8th bit) will cause a UnicodeError to be raised when getvalue() is called.'

[nackjicholson]

list(csv.reader(['"this is", "a test", "of the csv", "parser"']))[0] Boom!

[G M]

@rafaelc is more elegant but will give you wrong results