Parse a TSV file

I need to parse a file in TSV format (tab separated values). I use a regex to break down the file into each line, but I cannot find a satisfying one to parse each line. For now I've come up this:

(?<g>("[^"]+")+|[^\t]+)

But it does not work if an item in the line has more than 2 consecutive double quotes.

Here's how the file is formatted: each element is separated by a tabulation. If an item contains a tab, it is encased with double quotes. If an item contains a double quote, it is doubled. But sometimes an element contains 4 conscutive double quotes, and the above regex splits the element into 2 different ones.

Examples:

item1ok "item""2""oK"

is correctly parsed into 2 elements: item1ok and item"2"ok (after trimming of the unnecessary quotes), but:

item1oK "item""""2oK"

is parsed into 3 elements: item1ok, item and "2ok (after trimming again).

Has anyone an idea how to make the regex fit this case? Or is there another solution to parse TSV simply? (I'm doing开发者_如何学Go this in C#).

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You could use the TextFieldParser. This is technically a VB assembly, but you can use it even in C# by referencing the Microsoft.VisualBasic.FileIO assembly.

The example at the link above even shows using it on a tab-separated file.

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Instead of trying to build your own CSV/TSV file parser (or using String.Split), I'd recommend you have a look at "Fast CSV Reader" or "FileHelpers library".

I'm using the first one, and am very happy with it (it supports any separator characters, e.g. comma, semicolon, tab).

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Instead of using RegEx, maybe you could try the String.Split Method (Char[]) method.

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I don't know C# but this should do the trick (in python)

txt = 'item1ok\t"item""2""oK"\titem1oK\t"item""""2oK"\tsomething else'
regex = '''
(?:                    # definition of a field
 "((?:[^"]|"")*)"   # either a double quoted field (allowing consecutive "")
 |                  # or
 ([^"]*)            # any character except a double quote
)                      # end of field
(?:$|\t)               # each field followed by a tab (except the last one)
'''
r = re.compile(regex, re.X)
# now find each match, and replace "" by " and remove trailing \t
# remove also the latest entry in the list (empty string)
columns = [t[0].replace('""', '"') if t[0] != '' else t[1].strip() for t in r.findall(txt)][:-1]
print columns
# prints: ['item1ok', 'item"2"oK', 'item1oK', 'item""2oK', 'something else']