Shortest way to convert these bytes to int in python?

Question

I'm converting the following string to it's unsigned integer representation:

str = '\x00\x00\x00\x00\x00\x00\x01\xFF'

I can use struct.unpack('8B', str) to get the tuple representation (0,0,0,0,0,0,1,255), but what's the quickest/easiest way to convert this tuple to an int?

Right now, my code is

def unpack_str(s):
  i = r = 0
  for b in reversed(struct.unpack('8B', s)):
    r += r*2**i
    i++
  return r

But this is long and ugly, for such a simple function! There must be a better way! Can any SO python gurus help me to trim this down and python-ify it?

Answer 1

>>> struct.unpack('>q', s)[0]
511