Creating my own "integer" object in Python

Essentially I want to be able to do something like:

a = Integer(1)
a += 1
print a

And of course printing the number two as result. What methods do I need to create to get this behaviour in my Integer class?

Disclaimer: I'm not planning to use this for "real", just curious.

This is a simple and incomplete example. Look at methods __sub__, __div__ and so on.

class Integer(object):
    def __init__(self, val=0):
        self._val = int(val)
    def __add__(self, val):
        if isinstance(val, Integer):
            return Integer(self._val + val._val)
        return self._val + val
    def __iadd__(self, val):
        self._val += val
        return self
    def __str__(self):
        return str(self._val)
    def __repr__(self):
        return 'Integer(%s)' % self._val

Then

n = Integer()
print n
m = Integer(7)
m+=5
print m

EDIT fixed __repr__ and added __iadd__. Thanks to @Keith for pointing problems out. EDIT Fixed __add__ to allow addition between Integers.