Extracting information from files
Build a generator over the file to return just ints, then transpose the enumeration to get your X and Y, eg:

with open('testing.txt') as fin:
    lines = (int(line) for line in fin)
    total = next(lines)
    X, Y = zip(*enumerate(lines, 1))


Note X and Y will be tuples instead of lists, but you can convert them after if you wish.