如何使用Python 3使用if語句在計算器中進行減法和除法運算？

Question

所以我之前問過一個問題，為什么我在python 3.6.1中制作的計算器中的減法和除法不起作用。 你們中的許多人都慷慨地回答，但我沒有得到想要的答案。 抱歉，我應該更具體一些，但是有沒有辦法在while循環內添加某種if語句？ 這是我的代碼：

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，減法和除法有點相反，如果我嘗試輸入2個數字，9和3進行減法，我將得到-6，而除法則將得到0.33333333（1/3）。 抱歉，如果這是一個愚蠢的問題，因為在編碼方面我是一個完整的初學者。

Answer 1

對於加法和乘法順序無關緊要，即9 + 6 = 6 + 9和3 * 2 = 2 * 3。 但是減法和除法不是這樣，即9-6不等於6-9。

如果您要減去輸入的數字9和6，請執行以下操作：

對於第一個輸入：9，數字= 9＆diff = 0，所以diff =數字-diff = 9-0 = 9

對於第二個輸入：6，number = 6＆diff = 9所以diff = number-diff = 6-9 = -3

這不是我們的意圖

您的代碼稍作修改

# 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)

Answer 2

在看到您的代碼后，我為您准備了相同的代碼，並且使用了您的calc類，您很容易忘記鍵入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)))