[Tutor] CSV module?

[Liam Clarke]

Kent, 

As always, you are a beam of light upon the darkness of my illogicity
and/or ignorance.

You're right, I wasn't reopening the inputfile after doing
readlines(), which I was doing each time I opened the file! So, I
guess there's a pointer for each file object, that readline
increments.

If I wanted to reset that pointer for fileObject=file('erm.scc', 'r'),
could I just use

fileObject.seek(0)?


Thanks once again,

Liam Clarke

On Sat, 20 Nov 2004 20:40:13 -0500, Kent Johnson <kent37 at tds.net> wrote:
> Liam,
> 
> I can't be sure without seeing your whole program, but my guess is you
> either
> - didn't close the output file before opening for read, or
> - didn't re-open the input file between trying readlines() and reading
> with the csv reader, so the csv reader was just getting the end-of-file.
> 
> Anyway, here is a version of your snippets that works:
> 
> import csv
> 
> spreadS=[['A','B','C'],[1,2,3],[4,5,6]]
> dave=file('test.csv', 'w')
> henry=csv.writer(dave)
> henry.writerows(spreadS)
> dave.close()
> 
> x=file('test.csv','r')
> bob=csv.reader(x)
> for element in bob:
>       print element
> 
> 
> Kent
> 
> 
> 
> 
> Liam Clarke wrote:
> > Hi all,
> >
> > Trying to work the CSV module, and I'm not quite sure how to
> > input/output through it.
> >
> > I've worked out to output a CSV file that looks like -
> >
> > A B C
> > 1  2 3
> > 4  5 6
> >
> > you have to use a list like this -
> > spreadS=[['A','B','C'],[1,2,3],[4,5,6]], so each row is a separate
> > list.
> >
> > and then
> >
> > dave=file('test.csv', 'w')
> > henry=csv.writer(dave)
> >
> > and either
> >
> > for element in dave:
> >     henry.writerow(element)
> >
> > or just
> >
> > henry.writerows(dave).
> >
> > So writing is fine. But, if I were to reopen test.csv -
> >
> > x=file('test.csv','r')
> >
> > I can do this -
> >
> >
> >>>>print x.readlines()
> >
> > ['A,B,C\r\n', '1,2,3\r\n', '4,5,6\r\n']
> >
> > which is roughly what I expected.
> >
> > Howeever, if I were to do -
> >
> >
> >>>>bob=csv.reader(x)
> >
> >
> > And as per the Python docs -
> >
> > for element in bob:
> >      print element
> >
> > I get nothing.
> >
> > If I try bob.next(), I get 'StopIteration' which means that it's
> > reached the end of the file.
> >
> > So help? I'm probably doing something quite simple & silly, but the
> > documentation isn't much help (to me), and I've got not spreadsheet
> > software installed on this comp to check that my csv's are valid.
> >
> > I figure if I can pipe some data out through the CSV module and then
> > pipe it back in and nothing's changed then I'm doing OK.
> >
> > Regards,
> >
> > Liam Clarke
> > 
> _______________________________________________
> Tutor maillist  -  Tutor at python.org
> http://mail.python.org/mailman/listinfo/tutor
> 


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And with it comes the only basic human duty, to take the consequences.