一个简单的计算器程序的问题，输入数字零时似乎总是出现错误

Question

我是堆栈溢出网站、python 和整个编程的新手。如果这个问题的标题或正文不恰当，请原谅我。

我正在尝试用python创建一个简单的计算器程序，它只执行四种操作，即加法、减法（差）、乘法和除法。

这是我的代码：

print("Welcome to the calculator \n")

num1 = int(input("Enter the first number \n"))
num2 = int(input("Enter the second number \n"))

operation = (input("""Enter the symbol of the operation to be performed. Your choices are:
                                             +
                                             - (Difference)
                                             *
                                             /
\n """))

add = num1+num2

sub1 = num1-num2
sub2 = num2 - num1

product = num1*num2
quotient = num1 / num2


if operation == "-" :

    if num1 > num2:
        print(sub1)
    else:
        print(sub2)

elif operation == "+" :
    print(add)

elif operation == "*" :
    print(product)

elif operation == "/" :
    if num2 == 0:
        print("Sorry, can't divide a number by zero")
    else:
        print(quotient)

else:
    print("Please enter a valid operator from among the ones provided above")

一切运行良好，除了当我输入零作为 num2 时，无论我选择什么运算符，输出 这是：

Traceback (most recent call last):
  File "test4.py.txt", line 19, in <module>
    quotient = num1 / num2
ZeroDivisionError: division by zero

非常感谢您的帮助。谢谢！

Answer 1

求if条件内的商，而不是在检查num==0之前，否则zero的除法已经完成，导致错误。：

elif operation == "/" :
    if num2 == 0:
        print("Sorry, can't divide a number by zero")
    else:
        quotient = num1 / num2
        print(quotient)

Answer 2

quotient = num1 / num2

这就是给你错误的那一行。在计算 num1 / num2 之前，您应该检查 num2 是否为零。您可以按照以下方式进行操作，您的程序会正常运行。

quotient
if num2 == 0:
    quotient = None
else :
    quotient = num1 / num2

否则，您可以只声明商并在用户输入运算符时计算商。如果用户输入/，那么你可以检查是否num2==0，如果是，你可以给出错误信息。

工作代码 -

print("Welcome to the calculator \n")

num1 = int(input("Enter the first number \n"))
num2 = int(input("Enter the second number \n"))

operation = (input("""Enter the symbol of the operation to be performed. Your choices are:
                                             +
                                             - (Difference)
                                             *
                                             /
\n """))

add = num1+num2

sub1 = num1-num2
sub2 = num2 - num1

product = num1*num2
quotient = None     # Don't divide by num2 here or you will get error of divisionbyzero

if operation == "-" :

    if num1 > num2:
        print(sub1)
    else:
        print(sub2)

elif operation == "+" :
    print(add)

elif operation == "*" :
    print(product)

elif operation == "/" :
    if num2 == 0:
        print("Sorry, can't divide a number by zero")
    else:
        quotient = num1 / num2
        print(quotient)

else:
    print("Please enter a valid operator from among the ones provided above")

Answer 3

由于你是新手，我会更详细地解释这一点，以便你真正知道自己做错了什么

注意这几行

add = num1+num2

sub1 = num1-num2
sub2 = num2 - num1

product = num1*num2
quotient = num1 / num2

当您执行此操作时，它实际上是在执行计算并将其分配给相应的值（即 quotient = num1 / num2 实际上将执行计算并将结果存储在 quotient 变量中）。因此，无论您选择何种运算符，您每次都在进行每项计算。最好只有在选择了该运算符的情况下才分配值，如下所示。

print("Welcome to the calculator \n")

num1 = int(input("Enter the first number \n"))
num2 = int(input("Enter the second number \n"))

operation = (input("""Enter the symbol of the operation to be performed. Your choices are:
                                             +
                                             - (Difference)
                                             *
                                             /
\n """))


if operation == "-" :
    sub1 = num1-num2
    sub2 = num2 - num1
    if num1 > num2:
        print(sub1)
    else:
        print(sub2)

elif operation == "+" :
    add = num1+num2
    print(add)

elif operation == "*" :
    product = num1*num2
    print(product)

elif operation == "/" :
    if num2 == 0:
        print("Sorry, can't divide a number by zero")
    else:
        quotient = num1 / num2
        print(quotient)

else:
    print("Please enter a valid operator from among the ones provided above")

这部分只是一个建议。您还可以使用以下方法使您的差异操作更容易。

if operation == "-" :
    sub1 = num1-num2
    print(abs(sub1))

abs得到绝对值，基本去掉负数。

Answer 4

您应该在检查运算符后才计算结果（从而避免因试图除以零而导致的任何错误），这样您也可以避免不必要的计算：

elif operation == "/" :
    if num2 == 0: 
        print("Sorry, can't divide a number by zero")
    else:
        quotient = num1 / num2
        print(quotient)