Python素数计算器 - 不更新布尔值

Question

from sys import argv

def prime():
  for i in range(2,num):
      if num % i == 0:
          print(f"{num} can be divisible by {i}.")
          checker = False

num = int(input("Enter the number you want to check is prime: "))
checker = True

if num < 2:
    print(f"{num} is a prime number.")
elif num == 0:
    print(f"{num} is not a prime number.")
elif num > 0:
    prime()
    print(f"Is this number a prime - {checker}.")
else:
    print(f"Please write number larger than 0.")

大家好，我刚刚开始编写代码，这可能是一个非常简单的问题。我希望我的代码要么找到一个数字的因数，要么打印一个数字是否是素数——但我在“素数”函数中的布尔值永远不会更新为 False。不知道为什么！

谢谢。

Answer 1

您的prime() 函数没有“更新”到False 的原因是函数中没有return 语句。

有了它，函数看起来是这样的：

def prime():
  checker = True
  for i in range(2,num):
      if num % i == 0:
          print(f"{num} can be divisible by {i}.")
          checker = False
  return checker

更新后的代码如下所示：

from sys import argv

def prime():
  checker = True
  for i in range(2,num):
      if num % i == 0:
          print(f"{num} can be divisible by {i}.")
          checker = False
  return checker


num = int(input("Enter the number you want to check is prime: "))

if num < 2:
    print(f"{num} is a prime number.")
elif num == 0:
    print(f"{num} is not a prime number.")
elif num > 0:
    is_prime = prime()
    print(f"Is this number a prime - {is_prime}.")
else:
    print(f"Please write number larger than 0.")

但是，这不是解决您的问题的唯一方法：it's not recommended and frowned upon by many programmers as bad practice - 使用 global 语句（看起来这就是您最初尝试做的）。

有了它，函数看起来是这样的：

def prime():
  global checker
  for i in range(2,num):
      if num % i == 0:
          print(f"{num} can be divisible by {i}.")
          checker = False

更新后的代码如下所示：

from sys import argv

def prime():
  global checker
  for i in range(2,num):
      if num % i == 0:
          print(f"{num} can be divisible by {i}.")
          checker = False


num = int(input("Enter the number you want to check is prime: "))
checker = True

if num < 2:
    print(f"{num} is a prime number.")
elif num == 0:
    print(f"{num} is not a prime number.")
elif num > 0:
    prime()
    print(f"Is this number a prime - {checker}.")
else:
    print(f"Please write number larger than 0.")

Answer 2

def prime():
       global checker
       """ remaining logic as is"""

我认为这会奏效。 对不起，我在手机上写的格式。