Path: csiph.com!usenet.pasdenom.info!gegeweb.org!newsfeed.kamp.net!newsfeed.kamp.net!newsfeed.freenet.ag!news2.euro.net!newsgate.cistron.nl!newsgate.news.xs4all.nl!post.news.xs4all.nl!not-for-mail
Date: Mon, 11 Feb 2013 13:02:35 +0000
From: MRAB <python@mrabarnett.plus.com>
User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:17.0) Gecko/20130107 Thunderbird/17.0.2
MIME-Version: 1.0
To: python-list@python.org
Subject: Re: Error in reading and writing CSV format file in python
References: <mailman.1634.1360580421.2939.python-list@python.org> <5118e383$0$29985$c3e8da3$5496439d@news.astraweb.com> <CAFqGZRHPtHRR8Sa5EgzMBxL12PX_S5ko4N0St1r6S5LQb2V78g@mail.gmail.com>
In-Reply-To: <CAFqGZRHPtHRR8Sa5EgzMBxL12PX_S5ko4N0St1r6S5LQb2V78g@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: list
Reply-To: python-list@python.org
Newsgroups: comp.lang.python
Message-ID: <mailman.1644.1360587743.2939.python-list@python.org>
Lines: 88
NNTP-Posting-Host: 2001:888:2000:d::a6
Xref: csiph.com comp.lang.python:38675

On 2013-02-11 12:44, inshu chauhan wrote:
>
> On Mon, Feb 11, 2013 at 1:26 PM, Steven D'Aprano
> <steve+comp.lang.python@pearwood.info
> <mailto:steve+comp.lang.python@pearwood.info>> wrote:
>
>     inshu chauhan wrote:
>
>      > In the programme below I am trying to read two csv format files and
>      > process them and write a new file with some of theirs data.
>      >
>      > import csv
>      > f1_reader = csv.reader(open(r"Z:\Weka
>      > work\Feature_Vectors_Fullset_00.arff"))
>      > f2_reader = csv.reader(open(r"Z:\Weka
>      > work\Feature_Vectors_Fullset_00_noxy+class.arff"))
>      > nf = open(r"Z:\Weka work\classified_image00_withoutxy.arff", "w")
>      >
>      > while True:
>      >     l1 = f1_reader.next()
>      >     while len(l1) != 12:
>      >         l1 = f1_reader.next()
>      >     l2 = f2_reader.next()
>      >     while len(l2) != 11:
>      >         l2 = f2_reader.next()
>      >
>      >     ix = l1[0].strip()
>      >     iy = l1[1].strip()
>      >     classification = l2[8].strip()
>      >
>      >     print >> nf, ix, iy, classification
>      >
>      > nf.close()
>      >
>      > This programme is giving me this error now :
>      >
>      > Traceback (most recent call last):
>      >   File "Z:\Weka work\final_image_classificationwithoutxy.py",
>     line 16, in
>      > <module>
>      >     l2 = f2_reader.next()
>      > StopIteration
>      >
>      >
>      > what could be a possible reason to StopIteration ???
>
>     next() raises StopIteration when there is nothing else to return.
>
>
>     py> it = iter([1, 2, 3])
>     py> it.next()
>     1
>     py> it.next()
>     2
>     py> it.next()
>     3
>     py> it.next()
>     Traceback (most recent call last):
>        File "<stdin>", line 1, in <module>
>     StopIteration
>
>
>     You have reached the end of the file and there is nothing else for
>     the CSV
>     reader to return, so it raises StopIteration.
>
>
>
> But why does it has nothing to return so early before traversing the
> whole file ? Is there any way it can be corrected ?  And also the
> programme isn't writing anything to the file ?
>
Try adding some logging so that you can see what it's doing. A simple way
would be something like:

log_file = open(r"Z:\Weka work\log.txt", "w")

...

l1 = f1_reader.next()
print >> log_file, "Read from f1:", l1
print >> log_file, "Length is", len(l1)
while len(l1) != 12:
     l1 = f1_reader.next()
     print >> log_file, "Read from f1:", l1
     print >> log_file, "Length is", len(l1)

and so on.