LeetCode 191 Number of 1 Bits

Write a function that takes an unsigned integer and returns the number of ’1' bits it has (also known as the Hamming weight).

For example, the 32-bit integer ’11' has binary representation 00000000000000000000000000001011, so the function should return 3.

class Solution:    # @param n, an integer    # @return an integer    def hammingWeight(self, n):        a = str(bin(n))        l = []        for x in a:            l.append(x)        ans = 0        for x in l:            if x == '1':                ans += 1        return ans