Pythonic way to iterate over bits of integer

Question

Let's a=109 or 1101101 in binary. How do I iterate over bits of this number, eg: [64, 32, 8, 4, 1]

Answer 1

There's a trick for just getting the 1's out of the binary representation without having to iterate over all the intervening 0's:

def bits(n):     while n:         b = n & (~n+1)         yield b         n ^= b   >>> for b in bits(109):     print(b)   1 4 8 32 64 

Answer 2

My approach:

def bits(number):     bit = 1     while number >= bit:        if number & bit:            yield bit        bit <<= 1 

I don't think there is a builtin function for it.

I also wonder if there isn't a better approach to whatever you are doing. There's a good chance you don't really want to iterate over the bits like this. They may be a much better way.

Out of curiosity I ran some timing on the methods posted here, my results:

Winston 2.35238099098 F.J. 6.21106815338 F.J. (2) 5.21456193924 Sven 2.90593099594 Duncan 2.33568000793 freegnu 4.67035484314 

F.J. converts to a string, I'm guessing that hurts his performance. The various optimisation attempts help, but not enough Sven produces the reverse of everybody else, which might be an advantage if you really needed that. Duncan's approach wins speedwise (just barely)

Again with 340282366920938463463374607431768211457 instead of 109:

Winston 44.5073108673 F.J. 74.7332041264 Sven 47.6416211128 Duncan 2.58612513542 

Nice, Duncan! It should be noted that this is pretty much the best case for Duncan's method, so it won't always have this dramatic an advantage.