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