The error message is fairly self-explanatory. Your program expects  python split() 3 to yield 2 elements, but in your case, it is only yielding 1 element. This could be because the data is not in the format you expect, a rogue malformed line, or maybe an empty line - there’s no way to know.
To see what line is causing the issue, you could add some debug statements like this:
if len(line.split()) != 2:
    print line