问题就是求最大公因数
def largest_factor(n):
"""Return the largest factor of n that is smaller than n.
>>> largest_factor(15) # factors are 1, 3, 5
5
>>> largest_factor(80) # factors are 1, 2, 4, 5, 8, 10, 16, 20, 40
40
>>> largest_factor(13) # factor is 1 since 13 is prime
1
"""
i = 1
while i < n ** 1/2:
i += 1
if not n % i:
return n//i
return 1
这后面的循环内容没看明白，if not 是怎么用的，还有那个return n//i和return 1也不懂，能给讲讲吗