Number of 1 Bits

Difficulty: Easy

Write a function that takes an unsigned integer and returns the number of '1' bits it has(alse known as the Hamming weight).
For example, the 32-bit integer '11' has binary representation 00000000000000000000000000001011, so the function should return 3.

class Solution(object):
def hammingWeight(self, n):
    """
    :type n: int
    :rtype: int
    """
    weight = 0
    while n > 0:
        weight ++
        n &= (n -1)
    return weight