函数is_prime - 错误

Question

这是来自codeacademy.com的问题,我正在学习Python.所以我想要的是定义一个检查数字是否为素数的函数.如果是,则返回True.如果不是,则返回False.

这是我的代码:

def is_prime(x):
    lst = []       # empty list to put strings 'False' and 'True'

    for i in range(2,x): # starting at 2 and not including x (number 1 is a divisor of all numbers

        if x <= 2:           # [1] see bellow the explanation
            lst.append('False')
            break

        elif x % i == 0: # if x is divisible by i(number between 2 and not including x)
            lst.append('False')
            break        # break, because we already know x is not prime

        elif x % i > 0:
            lst.append('True') # x is not divisible by i

    if 'False' in lst:
        return False     #  x is not prime - return False

    else:
        return True  # 'True' is in lst, so x is prime - return True

print is_prime(-2) # [2] I get an error here. See below

[1] - 我做了这个条件,因为在codeacademy中它说:"提示记住:所有小于2的数字都不是素数!"

[2] - 当我跑步时,例如'print is_prime(11)'或'is_prime(6)'它可以正常运行.所以我提交了答案,但是codeacademy不接受它.它说:"你的函数在is_prime(-2)上失败.当它返回False时返回True."

Answer 1

让我们看看当你输入时会发生什么-2:

• range(2,-2)是空的,所以for循环永远不会运行.
• 因此,lst仍然[]是循环之后.
• 因此,'False' in lst是False
• 因此,return True执行.