Match CSV files for difference

[ichabod801]

This is a problem:

for row in file1_data:
    x = file1_data.index(row)
    file1_list.append(file1_data[x][1])

The second line is constantly searching through the list. My first thought was that it's much better to use enumerate:

for x, row in enumerate(file1_data):
    file1_list.append(file1_data[x][1])

But then I read the third line. file1_data[x] is row. They're the same thing. Why go to all that trouble?

for row in file1_data:
    file1_list.append(row[1])

Which is so simple it might as well be a list comprehension:

file1_list = [row[1] for row in file1_data]