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Re: Read csv file and create a new file

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On 28 Feb 2013 19:14:36 GMT, io <maroso@libero.it> declaimed the
following in gmane.comp.python.general:

> Hi,
> 
> i have to files. 
> 
> First file is a csv file
> Second file is a plain text file where each row has a value (text)
> 
> I want to be able to create a third file using data from the first file 
> excluding the values listed in the second file.
> 
> Example:
> 
> First file:
> -----------
> 
> mtgoxeur	12	24	36
> mtgoxusd	10	12	14
> mtgoxpln	2	4	6
> 
> 
> Second file:
> ------------
> 
> mtgoxusd
> 
> 
> 
> Third File (the resulting one) :
> --------------------------------
> 
> mtgoxeur	12	24	36
> mtgoxpln	2	4	6
> 
> 
> 
> Thanks to anyone that can help
> 

	This appears to be a variation of standard sort/merge operation. The
variation being that you /do not/ write lines of one file when they
match the other file.

	While an in-memory sort may be feasible (unless the data file is
extremely large) I would probably invoke your OS sort module on each
file...

	Then (pseudo-code, not executable python)

data = csvin.next()
key = keyfile.readln().strip()

while data and key:
	if data[0] < key:
		csvout.write(data)
		data = datafile.readln().strip()
	elif data[0] = key:
		data =csvin.next()
		#don't increment key to catch duplicates in data
	elif data[0] > key:
		key = keyfile.readln().strip()

while data:
	#no more keys to remove, copy rest of data file
	csvout.write(data)
	data = csvin.next()
-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
        wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/

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Read csv file and create a new file io <maroso@libero.it> - 2013-02-28 19:14 +0000
  Re: Read csv file and create a new file Neil Cerutti <neilc@norwich.edu> - 2013-02-28 19:32 +0000
  Re: Read csv file and create a new file Joel Goldstick <joel.goldstick@gmail.com> - 2013-02-28 14:34 -0500
  Re: Read csv file and create a new file Dave Angel <davea@davea.name> - 2013-02-28 14:35 -0500
  Re: Read csv file and create a new file io <maroso@libero.it> - 2013-02-28 19:51 +0000
    Re: Read csv file and create a new file Neil Cerutti <neilc@norwich.edu> - 2013-02-28 20:11 +0000
      Re: Read csv file and create a new file io <maroso@libero.it> - 2013-02-28 20:23 +0000
        Re: Read csv file and create a new file io <maroso@libero.it> - 2013-02-28 20:46 +0000
          Re: Read csv file and create a new file io <maroso@libero.it> - 2013-02-28 20:51 +0000
          Re: Read csv file and create a new file Dave Angel <davea@davea.name> - 2013-02-28 16:23 -0500
            Re: Read csv file and create a new file io <maroso@libero.it> - 2013-02-28 22:05 +0000
              Re: Read csv file and create a new file Dave Angel <davea@davea.name> - 2013-02-28 19:13 -0500
  Re: Read csv file and create a new file Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2013-02-28 21:04 -0500
    Re: Read csv file and create a new file io <maroso@libero.it> - 2013-03-04 19:04 +0000
      Re: Read csv file and create a new file Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-03-04 23:58 +0000

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