问质数

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我试着看看数字 2 ~ 12 中的素数是什么，我写了一些代码.但是在3"之后，即使存在11"，它也只会打印非质数".有什么问题?

I tried to see what is Prime number in number 2 ~ 12 , and I wrote some codes. But after '3', it only prints 'Not Prime number' even if '11' is there. What is the problem?

a=True for n in range(2,13): for i in range(2,n): if n % i ==0: a=False if a == False: print(n, ": Not prime.") else: print(n,": Prime")

推荐答案

您需要将每个 now 值的 a 重置为 True.另外 a == False 只是 not a (如 if a==True 是 if a)

You need to reset a to True for each now value. Also a == False is just not a (as if a==True is if a)

for n in range(2,13): a = True for i in range(2,n): if n % i ==0: a = False if not a: print(n, ": Not prime.") else: print(n,": Prime")

关于循环的一些建议

Some advices about the loop

• 在数字的平方根处停止
• 使用 break 在知道错误后停止循环
• 使用for/else，如果没有发现中断，则进入else

• stop at the square root of the number
• use a break to stop looping after knowing it's false
• use the for/else, if no break has been found it goes into the else

for n in range(2,13): for i in range(2,int(n**0.5)+1): if n % i ==0: print(n, ": Not prime.") break else: print(n,": Prime") 2 : Prime 3 : Prime 4 : Not prime. 5 : Prime 6 : Not prime. 7 : Prime 8 : Not prime. 9 : Not prime. 10 : Not prime. 11 : Prime 12 : Not prime.