如何使用 Python 3 在我的计算器中使用 if 语句进行减法和除法？答案

【问题标题】：How can I get subtraction and division in my calculator using Python 3 to work using an if statement?如何使用 Python 3 在我的计算器中使用 if 语句进行减法和除法？
【发布时间】：2017-07-30 16:21:17
【问题描述】：

所以我之前问了一个问题，为什么我在 python 3.6.1 中制作的计算器中的减法和除法不起作用。你们中的很多人都慷慨地回应了，但我没有得到我想要的答案。我很抱歉，因为我应该更具体一些，但是有没有办法让我在 while 循环中添加某种 if 语句？这是我的代码：

print("Welcome to Calculator!")

class Calculator:
    def addition(self,x,y):
        added = x + y
        return added
    def subtraction(self,x,y):
        subtracted = x - y
        return subtracted
    def multiplication(self,x,y):
        multiplied = x * y
        return multiplied
    def division(self,x,y):
        divided = x / y
        return divided

calculator = Calculator()

print("1 \tAddition")
print("2 \tSubtraction")
print("3 \tMultiplication")
print("4 \tDivision")
operations = int(input("What operation would you like to use?:  "))

x = int(input("How many numbers would you like to use?:  "))

if operations == 1:
    a = 0
    sum = 0
    while a < x:
        number = int(input("Please enter number here:  "))
        a += 1
        sum = calculator.addition(number,sum)
    print("The answer is", sum)
if operations == 2:
    s = 0
    diff = 0
    while s < x:
        number = int(input("Please enter number here:  "))
        s += 1 
        diff = calculator.subtraction(number, diff)
    print("The answer is", diff)
if operations == 3:
    m = 0
    prod = 1
    while m < x:
        number = int(input("Please enter number here:  "))
        m += 1
        prod = calculator.multiplication(number, prod)
    print("The answer is", prod)
if operations == 4:
    d = 0
    quo = 1
    while d < x:
        number = int(input("Please enter number here:  "))
        d += 1
        quo = calculator.division(number,quo)
    print("The answer is", quo)

基本上，减法和除法的工作方式相反，如果我尝试输入 2 个数字，9 和 3 进行减法，我会得到 -6，而除法我会得到 0.33333333(1/3)。对不起，如果这是一个愚蠢的问题，因为在编码方面我是一个完整的初学者。

【问题讨论】：

this post 不回答你的问题吗？
@ChristianDean 很好，他们都是非常好的答案，但我并没有真正得到我想要的答案
那么你在找什么？您需要清楚地说明您正在详细查看的答案四。否则，我们真的帮不上什么忙。
@ChristianDean 我得到了我想要的答案。我也确实说明了我正在寻找的答案，即在 while 循环中包含某种 if 语句。

标签： python calculator division python-3.6 subtraction

【解决方案1】：

对于加法和乘法顺序无关紧要，即 9+6=6+9 和 3*2=2*3。但减法和除法并非如此，即 9-6 不等于 6-9。

在您的情况下，输入 9 和 6 的减法：

对于第一个输入：9，number = 9 & diff = 0 所以 diff = number - diff = 9 - 0 = 9

对于第二个输入：6，number = 6 & diff = 9 所以 diff = number - diff = 6 - 9 = -3

这不是我们的意图

对代码稍作修改

# For Subtraction
if operations == 2:
    s = 0
    diff = 0
    while s < x:
        number = int(input("Please enter number here:  "))
        s += 1
        if (s==1):
            diff=number
        else:
            diff = calculator.subtraction(diff, number)
    print("The answer is", diff)

#For Division
if operations == 4:
    d = 0
    quo = 1
    while d < x:
        number = int(input("Please enter number here:  "))
        d += 1
        if (d==1):
            quo=number
        else:
            quo = calculator.division(quo,number)
    print("The answer is", quo)

【讨论】：

【解决方案2】：

看到你的代码后，我为你制作了这个，它是一样的，我使用你的 calc 类很容易忘记输入 Float

class Calculator:
    def addition(self,x,y):
        added = x + y
        return added
    def subtraction(self,x,y):
        subtracted = x - y
        return subtracted
    def multiplication(self,x,y):
        multiplied = x * y
        return multiplied
    def division(self,x,y):
        divided = x / y
        return divided

calculator = Calculator()
num1 = raw_input('First Number >')
num2 = raw_input('Second Number >')
print("1 \tAddition")
print("2 \tSubtraction")
print("3 \tMultiplication")
print("4 \tDivision")
operations = raw_input('Select operation number>')

if int(operations)== 1:
    print (calculator.addition(float(num1),float(num2)))
if int(operations)== 2:
    print (calculator.subtraction(float(num1),float(num2)))
if int(operations)== 3:
    print (calculator.multiplication(float(num1),float(num2)))
if int(operations)== 4:
    print (calculator.division(float(num1),float(num2)))

【讨论】：