Is Power of Two
by Isai Damier, Android Engineer @ Google

#======================================================================
# Author: Isai Damier
# Title: Is Power of Two
# Project: geekviewpoint
# Package: algorithms
#
# Statement:
#   Indicate whether the given integer n is a power of two.
#
# Sample Input:  16
# Sample Output: true
#
# Technical Details:
#   A number that is a power of two only has one set bit: 0 = 0; 2 = 10;
#   4 = 100; 8 = 1000; 16 = 10000; etc. Therefore checking whether a
#   number is a power of two is as simple as clearing the lowest set bit
#   and then checking that the result is equal to zero.
#   (ref http://www.geekviewpoint.com/python/bitwise/clear_lowest_bit)
#====================================================================== 
 def isPowerOfTwo( n ):
  return 0 == ( n & ( n - 1 ) )

import unittest
from algorithms import bitwise as bits

class Test( unittest.TestCase ):

    def testIsPowerOfTwo( self ):
        for i in range( 1, 31 ) :
          self.assertTrue( bits.isPowerOfTwo( 2 ** i ) )