Chaning self?

[Miki Tebeka]

Hello,

I'm trying to create a class which is a bit array. I've done the following:
class bitarray(long):
    def __init__(self, value):
        super(long, self).__init__(value)

    def __getitem__(self, index):
        if self & (1 << index):
            return 1
        else:
            return 0

    def __setitem__(self, index, value):
        if value not in (0, 1):
            raise ValueError("must be 0 or 1")
        if value:
            self |= (1 << index)
        else:
            self &= (~ (1 << index))

However the __setitem__ does not work:
>>> b = bitarray(5)
>>> b[0]
1
>>> b[1]
0
>>> b[2]
1
>>> b[0] = 0
>>> b
5L
>>> b[0]
1

What am I missing?

Thanks.
Miki