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MathGroup Archive 2004

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Re: Import[filename,"CSV"] is so slooooooooow!

  • To: mathgroup at
  • Subject: [mg45935] Re: [mg45920] Import[filename,"CSV"] is so slooooooooow!
  • From: Tomas Garza <tgarza01 at>
  • Date: Fri, 30 Jan 2004 04:16:03 -0500 (EST)
  • References: <>
  • Sender: owner-wri-mathgroup at

You might try playing around with options NullWords and WordSeparators in
ReadList. I have a file with about 300,000 text records which is read in
about 8 seconds. If you have a numeric file, use Number instead of Word:

AbsoluteTiming[test = ReadList["c:\myfile.txt", Word,
     NullWords -> True, WordSeparators -> {",", "\t"}, RecordLists ->
True]; ]

{8.7025136 Second,Null}

Tomas Garza
Mexico City
----- Original Message ----- 
From: "1.156" <rob at>
To: mathgroup at
Subject: [mg45935] [mg45920] Import[filename,"CSV"] is so slooooooooow!

> Hi.
> I'm getting data in CSV files to analyze.  With the new ver. 4.2 I can
> get these data in nicely using
> data = Import["filename", "CSV"]
> but it takes 30 seconds to get in a 100kB file.  And I've got to do some
> much longer files.
> On the other hand, if I change all the comma delimiters to spaces, I can
> get the data in using
> inFile = OpenRead["filename"];
> y = ReadList[inFile, Number, RecordLists -> True];
> Close[inFile];
> This pulls in the same 100kB file in a second or so.  But, doing this
> comma to space conversion is truly slow (using Word).
> So, can someone out there enlighten me with a suggestion on how to
> either speed up Import or get ReadList to handle comma delimiters?
> Thanks and Regards, Rob

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