Python Error:(IndexError: list index out of range) on trying to write a line to CSV

Question

I'm trying to split a CSV file into multiple files. The code works fine if I use it from command line.

I'm running Python csv_splitterFunction.py C:\Users\xlViki\Desktop\Python\Journal.py in cmd

import sys  

number_of_outfiles = 4  

if __name__ == "__main__":  
    k = []  
    for i in range(number_of_outfiles):  
        k.append(open(r'C:\Users\xlViki\Desktop\Python\Output_' + str(i) + '.csv','w'))  
    with open(sys.argv[1]) as inf:  
        for i, line in enumerate(inf):  
            if line[-1] == '\n': line = line[:-1]  
            if i == 0:  
                headers = line  
                [x.write(headers + '\n') for x in k]  
            else:
                k[i % number_of_outfiles].write(line + '\n')  
    [x.close() for x in k]

But I'm getting a list out of range error when I'm trying to convert the code into a function like below and running in the Python shell (pressing F5 in IDLE):

def Main(filepath):
    import sys  
    number_of_outfiles = 4  

    if __name__ == "__main__":  
        k = []  
        for i in range(number_of_outfiles):  
            k.append(open(r'C:\Users\xlViki\Desktop\Python\Output_' + str(i) + '.csv','w'))
            print (r'C:\Users\xlViki\Desktop\Python\Output_' + str(i))
            with open(filepath) as inf:  
                for i, line in enumerate(inf):  
                    if line[-1] == '\n': line = line[:-1]  
                    if i == 0:  
                        headers = line  
                        [x.write(headers + '\n') for x in k]  
                    else:
                        print(i)
                        print(k[0])
                        k[i % number_of_outfiles].write(line + '\n')  
            [x.close() for x in k] 


Main(r'C:\Users\xlViki\Desktop\Python\Journal.csv')

This is the output I'm receiving:

C:\Users\xlViki\Desktop\Python\Output_0
1
<_io.TextIOWrapper name='C:\\Users\\xlViki\\Desktop\\Python\\Output_0.csv' mode='w' encoding='cp1252'>
Traceback (most recent call last):
  File "<pyshell#0>", line 1, in <module>
    Main(r'C:\Users\xlViki\Desktop\Python\Journal.csv')
  File "C:\Users\xlViki\Desktop\Python\csv_splitterFunction.py", line 22, in Main
    k[i % number_of_outfiles].write(line + '\n')
IndexError: list index out of range

Can you please help me convert this code into a function?

JHobern · Accepted Answer · 2015-08-25 22:36:24Z

1

The error message is telling you that the list index out of range exception occurred on line 22, k[i % number_of_outfiles].write(line + '\n'). This line is going to try and access k[0], k[1], k[2], and k[4], but on the first iteration through the loop you have only put 1 element into k, so you can only access k[0]. The solution to this is to open all of the files and put them in k before you enter the loop starting with with open(filepath) as inf:. Additionally, you have used i as a variable twice, if you intend to keep the loops nested you should change one of their names, otherwise you can just unindent with open(filepath) as inf:.

answered Aug 25, 2015 at 22:36

JHobern

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1 Comment

xlViki Over a year ago

Thanks a lot! that did it. Now when I know the answer, the difference in both codes looks so obvious. Thanks for the explanation as well.

MHardwick · Accepted Answer · 2015-08-25 22:28:41Z

1

Looks like you need to unindent everything from with open(filepath) as inf: on. The first file is opening, but then the second line attempts to write to the second file before it's even open.

answered Aug 25, 2015 at 22:28

MHardwick

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1 Comment

xlViki Over a year ago

Thanks a lot! That was it, I unindented the code and it just works!

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