Regular expression for parsing CSV

Question

I'm trying to parse a CSV file in C#. Split on commas (,). I got it to work with this:

[\t,](?=(?:[^\"]|\"[^\"]*\")*$)

Splitting this string:

2012-01-06,"Some text with, comma",,"300,00","143,52"

Gives me:

2012-01-06
"Some text with, comma"

"300,00"
"143,52"

But I can't figure out how to lose the "" from the output so I get this instead:

2012-01-06
Some text with, comma

300,00
143,52

Any suggestions?

Which particular language/framework/OS/tool? There's lots of different regexp parsers out there :-) — Chris J, Jul 06 '12 at 14:45

Chris Dargis · Answer 1 · 2012-07-06T15:57:10.343

2

Why are you using regular expressions for this? Ensuring the file is well-formed?

You can use String.Replace()

String s = "Some text with, comma";
s = s.Replace("\"", "");

// After matched
String line = 2012-01-06,"Some text with, comma",,"300,00","143,52";
String []fields = line.Split(',');
for (int i = 0; i < fields.Length; i++)
{
   // Call a function to remove quotes
   fields[i] = removeQuotes(fields[i]);
}

String removeQuotes(String s)
{
   return s.Replace("\"", "");
}

edited Jul 06 '12 at 15:57

answered Jul 06 '12 at 14:52

Chris Dargis

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Didn't you see his sample string? 2012-01-06,"Some text with, comma",,"300,00","143,52" – aquinas Jul 06 '12 at 15:12
@aquinas: Why did you feel important to mention this? As far as I can tell, the OP is just trying to remove any and all quotes from a string. – Chris Dargis Jul 06 '12 at 15:30
No I'm trying to split the fields, witch is working but I would like to get rid of the " from the result. – Kristofer Källsbo Jul 06 '12 at 15:33
@Kallsbo: So after the split, can you call a function to remove the quotes from each element in the array? – Chris Dargis Jul 06 '12 at 15:38
@VanDarg, fair enough point. The title of the question is a bit misleading. Changed my vote. – aquinas Jul 06 '12 at 15:59
The only issue with this solution is what happens to embedded double quotes? – aquinas Jul 06 '12 at 16:19
@aquinas: Good point, all quotes are removed in this solution. Preserving embedded quotes would require something much more custom, but is certainly possible. – Chris Dargis Jul 06 '12 at 16:29

score 2 · Accepted Answer · edited May 23 '17 at 10:32

2

If you are trying to parse a CSV and using .NET, don't use regular expressions. Use a component that was created for this purpose. See the question CSV File Imports in .Net.

I know the CSV specification looks simple enough, but trust me, you are in for heartache and destruction if you continue down this path.

edited May 23 '17 at 10:32

Community

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answered Jul 06 '12 at 14:55

iamkrillin

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This was really the way to go! Thank you! – Kristofer Källsbo Jul 07 '12 at 17:13

score 2 · Answer 3 · answered Jul 06 '12 at 16:14

So, something like this. Again, I wouldn't use RegEx for this purpose, but YMMV.

var sp = Regex.Split(a, "[\t,](?=(?:[^\"]|\"[^\"]*\")*$)")
     .Select(s => Regex.Replace(s.Replace("\"\"","\""),"^\"|\"$","")).ToArray();

So, the idea here is that first of all, you want to replace double double quotes with a single double quote. And then that string is fed to the second regex which simply removes double quotes at the beginning and end of the string.

The reason for the first replace is because of strings like this:

var a = "1999,Chevy,\"Venture \"\"Extended Edition, Very Large\"\" Dude\",\"\",\"5000.00\"";

So, this would give you a string like this: ""Extended Edition"", and the double quotes need to be changed to single quotes.

Regular expression for parsing CSV

3 Answers3