Reading ints line from a file in Python
No need for split (you can use readlines). But no need for readlines, for that matter:

def read_integers(filename):
    with open(filename) as f:
        return map(int, f)


or, if that’s more to your fancy:

def read_integers(filename):
    with open(filename) as f:
        return [int(x) for x in f]


A file object is simply iterable in Python, and iterates over its lines.

Note that, contrary to what I said earlier, wrapping the file object in a with block is highly recommended. Python doesn’t actually guarantee (although it recommends it) that objects are disposed of automatically at the end of the scope. Worse, it’s not guaranteed that a file object that is collected actually closes the underlying stream.

(Note that I’ve adapted the method name to Python conventions.)