Error in reading and writing CSV format file in python

[inshu chauhan]

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 ???


I checked the syntax and usage of this module looks alright to me , but
then why this error ?


Thankyou in Advance
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