Reading data from 2 different files and writing to a single file

[inshu chauhan]

On Mon, Jan 28, 2013 at 6:05 PM, Dennis Lee Bieber <wlfraed at ix.netcom.com>wrote:

> On Mon, 28 Jan 2013 14:31:31 +0100, inshu chauhan
> <insideshoes at gmail.com> declaimed the following in
> gmane.comp.python.general:
>
> > In the code below I am trying to read 2 files f1 and f2 , extract some
> data
> > from them and then trying to write them into a single file that is 'nf'.
> >
> > import cv
> > f1 = open(r"Z:\modules\Feature_Vectors_300.arff")
> > f2 = open(r"Z:\modules\Feature_Vectors_300_Pclass.arff")
> > nf = open(r"Z:\modules\trial.arff", "w")
> >
> >
> > for l in f1:
> >     sp = l.split(",")
>
>         If you are going to be splitting on commas, you might want to read
> up on the csv (comma separate values) module
>

The  csv module has many fuctions but not of much use to me and it makes my
programme slower

>
> >
> >     if len(sp)!= 12:
> >         continue
> >     else:
>
>         Given the apparent block structure, you could drop the
> continue/else, and more cleanly just use
>

Yeah, Thats Right

>
>                 if len(sp) == 12:
> >         ix = sp[0].strip()
> >         iy = sp[1].strip()
> >         print ix, iy
> >
> >        for s in f2:
>
>         It's been mentioned that the indentation is wrong here
>

I dont know why the indentation is wrong ?

>
> >             st = s.split(",")
> >
>         csv module again
>
> >             if len(st)!= 11:
> >                 continue
> >             else:
>
>         I'm tempted to repeat the comment on reversing the conditional BUT
>
> >                 clas = st[10].strip()
> >
> >              print ix, iy, clas
> >              print >> nf, ix, iy, clas
> >
>         The indentation of the print statements is not aligned with the
> previous assignment -- the effect is the same however as everything
> under the else is executed anyway.
>
>         But as has also been mentioned, ignoring indentation, the apparent
> algorithm you have here is going to process every line of f2 for the
> first line of f1 -- and then for later lines in f1 it will find f2 is at
> the end of file, and do nothing. If it is supposed to process every line
> of f2 for each line of f1, you'll need to rewind f2.
>

For that I added 'Break' statement as suggested by Chris in above mails.

>
>         If you mean to match one line of f1 with one line of f2, you do not
> want nested loops. But now you have to define the behavior if one of the
> two files is correct length and the other is not? Do you skip both or
> read the next line from the wrong length file? And how will you handle
> files with different numbers of records.
>

Yes , actually my Prog was like this :
for l in f1:
    sp = l.split(",")

    if len(sp)!= 12:
        continue
    else:
        ix = sp[0].strip()
        iy = sp[1].strip()


for s in f2:
    st = s.split(",")

    if len(st)!= 11:
        continue
    else:
        clas = st[10].strip()

    print ix, iy, clas
    print >> nf, ix, iy, clas
    break


f1.close()
f2.close()
nf.close()

I actually dont want nested loops but cant find another way to achieve what
I want, But for these files I am sure that they have equal lengths, thats
why I am taking the risk of using nested loops.. Can you suggest any
different way to go around this problem , which could be flexible and
non-errorneous ?


>
>
>
> --
>         Wulfraed                 Dennis Lee Bieber         AF6VN
>         wlfraed at ix.netcom.com    HTTP://wlfraed.home.netcom.com/
>
> --
> http://mail.python.org/mailman/listinfo/python-list
>
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