Bitwise operations in class inheriting int

Question

I've inherited from int, because I wanted to implement a simple interface for bitwise operations. Due to the non mutability of int, I have to use the integer member functions like int.__and__, ... .

class Bitset(int)
    ...
    def __setitem__(self, index, value):
        if value:
            self.__ior__(1 << int(index))
        else:
            self.__iand__(~(1 << int(index)))

In one of my memberfunctions I want to use the |= and &= functions, but the integer has no __ior__ and __iand__ member functions. So my question is how can I solve this problem?.

Edit:

I dont want to simplify binary operations, I'd like to manipulate the bits of an integer. E.g.

a = Bitset(0)
a[0]
>>>0
a[0] = 1
a[0]
>>>1

But I didn't wan't to reimplement every integer operation, which should still work as well. If I wrap an internal integer I've got to do that. E.g

a = Bitset(0)
a += 1

should still work.

You can have the simple interface without inheriting from `int`. — martineau, Aug 06 '12 at 09:24
See question [increment int object](http://stackoverflow.com/questions/1135335/increment-int-object). — martineau, Aug 06 '12 at 09:51

score 1 · Answer 1 · answered Aug 06 '12 at 09:55

There is already simple interfaces for bitwise operations (see http://docs.python.org/reference/expressions.html#summary) e.g :

4 >> 1
# 2

You don't have __ior__ and __iand__ but you do have __and__ and __or__. But I suspect that what you want is actually __ror__ and __rand__ which implement bitwise operations. Integers do have those last magic methods. On magic methods see : http://www.rafekettler.com/magicmethods.html#numeric

See also : http://wiki.python.org/moin/BitwiseOperators

martineau · Accepted Answer · 2012-08-06T23:24:52.930

1

ints aren't subscriptable as well as being immutable, so you can't write a working __setindex__() method. It seems like what describing is basically a mutable bit-vector class, such as this one which appears to have been written by Guido. You can use the provided __int__() and __long__() methods to convert it an integer value (although I don't believe you need the latter any more).

edited Aug 06 '12 at 23:24

answered Aug 06 '12 at 23:13

martineau

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Bitwise operations in class inheriting int

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