python - why loop did not execute else -

import csv path1=r'/users/desktop/forks.csv' path2=r'/users/desktop/forks1.csv' outdata=[] count=0 i=0 open(path1,'rb') input: reader=csv.reader(input) row in reader:     if i==0:         i=i+1         outdata.append(row)         continue     if int(row[5])>0:         row.append(1)         outdata.append(row)         count=count+1         print count     else:          row.append(0)         outdata.append(row)         count=count+1 print count open (path2,'wb') output:   writer=csv.writer(output,delimiter=',')   writer.writerows(outdata) 

i have large table, want add column boolean value each row. if column 6 lager 0, should 1. if 0, should zero. loop stop @

58542 58543 58544 58545 58546 58547 58548 traceback (most recent call last): file "/users/documents/workspace/datamining/opensource/label.py", line 18, in <module> if int(row[5])>0: valueerror: invalid literal int() base 10: '' 

the information in table below, means else loop did not execute. test in small table,the code works.i don't know why cannot work in large dataset?

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58547                1 58548                1 58549                0 58550                0 

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valueerror: invalid literal int() base 10: '' 

you're passing empty value argument int. int cannot convert empty value integer.