Is there a way to get the largest integer one can use in Python?

Python has arbitrary precision integers so there is no true fixed maximum. You're only limited by available memory.

In Python 2, there are two types, int and long. ints use a C type, while longs are arbitrary precision. You can use sys.maxint to find the maximum int. But ints are automatically promoted to long, so you usually don't need to worry about it:

sys.maxint + 1

works fine and returns a long.

sys.maxint does not even exist in Python 3, since int and long were unified into a single arbitrary precision int type.