一个简单的计算器程序的问题，输入数字零时似乎总是出错

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 body 不恰当，请原谅我。

我正在尝试在 python 中创建一个简单的计算器程序，它只执行四种运算，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")

一切正常，除了当我输入 0 作为 num2 时，无论我 select 是什么运算符，输出这是：

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

帮助很大appreciated.Thanks！

Answer 1

求 if 条件内的商，而不是在检查 num==0 之前，否则除以 zero 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

您应该在检查运算符后才计算结果（从而避免尝试除以零而导致的任何错误），这样您也将避免不必要的计算：

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

Answer 3

quotient = num1 / num2

这是给您错误的那一行。在计算 num1 / num2 之前，您应该检查 num2 是否为零。您可以按如下方式进行，您的程序将运行良好。

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

否则你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 4

既然你是新手，我会更详细地解释这一点，这样你就知道你做错了什么

注意这些行

add = num1+num2

sub1 = num1-num2
sub2 = num2 - num1

product = num1*num2
quotient = num1 / num2

当你这样做时，它实际上是在执行计算并将其分配给相应的值（即 quotient = num1 / num2 将实际进行计算并将结果存储在商变量中）。因此，无论您选择哪种运算符，您每次都在进行所有计算。最好仅在如下所示选择了该运算符时才分配值。

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差分操作更容易。

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

abs取绝对值，基本去掉负数。

一个简单的计算器程序的问题，输入数字零时似乎总是出错

Problem with a simple calculator program where an error always seems to occur when entering the number zero

python-3.x

python-3.6

工作代码-