LC-Prime Number of Set Bits in Binary Representation

class Solution(object):
def countPrimeSetBits(self, L, R):
"""
:type L: int
:type R: int
:rtype: int
"""
def isPrime(n):
if n <= 1:
return False
i = 2
while i * i <= n:
if n % i == 0:
return False
i += 1
return True
count = 0
for x in range(L,R+1):
num_1 = bin(x).count('1')
if isPrime(num_1):
count += 1
return count

Sol = Solution()
print Sol.countPrimeSetBits(9,15)