CSV module: incorrectly parsed file.

Steve Holden steve at holdenweb.com
Mon Feb 18 06:31:03 CET 2008


7stud wrote:
> On Feb 17, 9:11 pm, 7stud <bbxx789_0... at yahoo.com> wrote:
>> On Feb 17, 7:09 pm, Christopher Barrington-Leigh
>>
>>
>>
>> <christophe... at gmail.com> wrote:
>>> Here is a file "test.csv"
>>> number,name,description,value
>>> 1,"wer","tape 2"",5
>>> 1,vvv,"hoohaa",2
>>> I want to convert it to tab-separated without those silly quotes. Note
>>> in the second line that a field is 'tape 2"' , ie two inches: there is
>>> a double quote in the string.
>>> When I use csv module to read this:
>>> import sys
>>> outf=open(sys.argv[1]+'.tsv','wt')
>>> import csv
>>> reader=csv.reader(open(sys.argv[1], "rb"))
>>> for row in reader:
>>>     outf.write('\t'.join([rr.strip() for rr in row]) +'\n')
>>> it mangles it, messing up the double double-quote.
>>> Can anyone help me? How do I use CSV to get it right?
>>> Tjhanks!
>>> c
>> Try this:
>>
>> infile = open('data.txt')
>> outfile = open('outfile.txt', 'w')
>>
>> for line in infile:
>>     pieces = line.strip().split(',')
>>
>>     data = []
>>     for piece in pieces:
>>         if piece[0] == '"':
>>             data.append(piece[1:-2])
>>         else:
>>             data.append(piece)
>>
>>     out_line = '%s\n' % '\t'.join(data)
>>     outfile.write(out_line)
> 
> Whoops.  The line:
> 
> data.append(piece[1:-2])
> 
> should be:
> 
> data.append(piece[1:-1])
> 
Even when you have done all this you will still have problems. As Andrew 
pointed out the form is ambiguous, and you'd just better hope none of 
your data items look like

   Nails 2", soldiers for the use of

because then you will be completely screwed. So there's a need for a 
certain amount of visual scrutiny of the data: I would definitely write 
a validation program first that tries to read the data and catches any 
exceptions like unmatched quotes or the wrong number of items in a line. 
If there aren't too many (and there usually aren't) just edit them out 
of your input data by hand.

If this is to be a regular task then you'll have to program to recognize 
and correct the common error cases.

regards
  Steve

-- 
Steve Holden        +1 571 484 6266   +1 800 494 3119
Holden Web LLC              http://www.holdenweb.com/




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