def primenumber(start,end):if start>=2:for n in range(start,end+1):for x in range(start,n):if n % x == 0:print(n,'equals',x,'*',n//x)breakelse:print(n,"is a prime number")
print( primenumber (2 , 10) )
运行结果：
2 is a prime number
3 is a prime number
4 equals 2 * 2
5 is a prime number
6 equals 2 * 3
7 is a prime number
8 equals 2 * 4
9 equals 3 * 3
10 equals 2 * 5
None
注意 none 在函数本身没有return，print后就会出现none 大概就是这个意思了