bit count or bit set && Python3

[Christian Gollwitzer]

Am 25.10.12 16:47, schrieb Charles Hixson:
> In Python3 is there any good way to count the number of on bits in an
> integer (after an & operation)?
> Alternatively, is there any VERY light-weight implementation of a bit
> set?  I'd prefer to use integers, as I'm probably going to need
> thousands of these, if the tests work out.  But before I can test, I
> need a decent bit counter.  (shift, xor, &, and | are already present
> for integer values, but I also need to count the number of "true" items
> after the logical operation.  So if a bitset is the correct approach,
> I'll need it to implement those operations, or their equivalents in
> terms of union and intersection.)
>
> Or do I need to drop into C for this?
>

There is a very geeky algorithm with only a few integer operations.

Checkout
http://graphics.stanford.edu/~seander/bithacks.html#CountBitsSet64

for a C version. Maybe the same thing is equally fast when ported to 
Python.

	Christian