Python3实现求质因数

import math
x = input("请输入一个整数，例如demo(15):\n")
def demo(n):
     r = []
     l = int(n/2 + 1)
     for i in range(2,l):
          if n % i == 0:
               k = int (math.sqrt(i) + 1)
               if k == 2:
                    r.append(i)
               else:
                    for j in range(2,k):
                         if i % j == 0:
                              break
                         else:
                              r.append(i)              
     return r