Reading from and Writing to CSV files
<p>I am struggling with Python 2.7.10.  I’m trying to create a program that will eventually open a CSV file, read numbers from the file, perform calculations with the numbers and write back to the CSV file.</p>

<p>The code (i.e. the calculations) is not finished, I just wanted to try a few small bits so I could start to identify problems.  The data in the CSV file looks like this:</p>

<pre><code>['110000,75000\n', '115000,72500\n', '105000,85250\n', '100000,70000']
</code></pre>

<p>One thing that I am having issues with is properly converting the CSV strings to numbers and then telling Python what row, column I want to use in the calculation; something like Row(0), Column(0) – Row(1) Column(1).</p>

<p>I have tried a few different things but its seems to crash on the converting to numbers bit.  Error message is <code>TypeError int() argument must be a string or a number, not list</code> OR <code>IOError File not open for string</code> – depending on what I have tried.  Can someone point me in the right direction?</p>

<pre><code>import csv

def main():
    my_file = open('InputData.csv','rU')
    #test = csv.writer(my_file, delimiter=',')

    file_contents = my_file.readlines()
    print file_contents

    for row in file_contents:
        print row

    #convert to numbers
    #val0 = int(file_contents.readlines(0))
    #val1 = int(file_contents.readlines(1))
    #val0 = int(my_file.readlines(0))
    #val1 = int(my_file.readlines(1))

    #perform calculation
    #valDiff = val1 - val0

    #append to third column, may need to be in write file mode, num to strings
    #file_contents.append
    my_file.close()

main()
</code></pre>