python OOP if语句需要垃圾邮件和未定义的变量

Question

在我的程序中，我有一个 if 语句作为我的第一个 main，但是每当输入字母时，它需要您再输入几次才能起作用，然后如果它起作用，则变量 num3 和 den3。

class menu:
    def question():
        prnt = print("Which equation would like to do? \n A: Inverse the fracion \n B: Add 2 fractions \n C: Subtract 2 fractions \n D: Multiply 2 fractions \n E: Divide 2 fractions \n F: Square a fraction \n")

    def ask():
        ask = input("")
        return ask

class fractions:
    def numerator():
        ask = menu.ask()
        if ask == "b" or menu.ask() == "B" or ask == "C" or ask == "c" or ask == "D" or ask == "d" or menu.ask() == "e" or menu.ask() == "e":
            num1 = int(input("What is the first numerator? \n"))
            num2 = int(input("What is the second numerator? \n"))
            return num1
            return num2

        elif ask == "a" or ask == "A" or ask == "f" or ask == "F":
            num1 = int(input("What is the numerator? \n"))
            return num1

    def denominator():
        ask = menu.ask()
        if mask == "b" or ask == "B" or ask == "C" or ask == "c" or ask == "D" or menu.ask() == "d" or menu.ask() == "e" or menu.ask() == "e":
            den1 = int(input("What is the first denominator? \n"))
            den2 = int(input("What is the second denominator? \n"))
            return den1
            return den2

        elif ask == "a" or ask == "A" or ask == "f" or ask == "F":
            den1 = int(input("What is the denominator? \n"))
            return den1

class math():
    def math1(a,b):
            num3 = den1
            den3 = num1
            return num3
            return den3

    def math2(a,b):
        if den1 == den2:
            num3 = num1 + num2
            den3 = den1
            return num3
            return den3

        if den1 != den2:
            num1 = num1 * den2
            num2 = num2 * den1
            den3 = den1 * den2
            num3 = num1 + num2
            return num3
            return den3

    def math3(a,b):
        if den1 == den2:
            num3 = num1 - num2
            den3 = den1
            return num3
            return den3

        elif den1 != den2:
            den3 = den1 * den2
            num1 = num1 * den2
            num2 = num2 * den1
            num3 = num1 - num2
            return num3
            return den3

    def math4(a,b):
            num3 = num1 * num2
            den3 = den1 * den2
            return num3
            return den3

    def math5(a,b):
            num3 = num1 * den2
            den3 = den1 * num2
            return num3
            return den3   

    def math6(a,b):
            num3 = num1.fractions().numerator() ** 2
            den3 = den1.fractions().denominator() ** 2
            return num3
            return den3            

    def reduce(a,b):
        maxnum = 1000
        while maxnum > 0:
            if num3 % maxnum == 0 and den3 % maxnum == 0:
                num3 = num3 / maxnum
                den3 = den3 / maxnum
            maxnum = maxnum - 1
        return num3
        return den3

def main():
    start = menu.question()
    ask = menu.ask()

    Numer = fractions.numerator()

    Duner = fractions.denominator()

    if menu.ask() == "A" or menu.ask() == "a":
       math.math1(Numer, Duner)
        num3 = math.math1(num3)
        den3 = math.math1(den3)

    elif menu.ask() == "B" or menu.ask() == "b":
        math.math2(Numer, Duner)
        num3 = math.math2(num3)
        den3 = math.math2(den3)

    elif menu.ask() == "C" or menu.ask() == "c":
        math.math3(Numer, Duner)
        num3 = math.math3(num3)
        den3 = math.math3(den3)

   elif menu.ask() == "D" or menu.ask() == "d":
       math.math4(Numer, Duner)
       num3 = math.math4(num3)
       den3 = math.math4(den3)

    elif menu.ask() == "E" or menu.ask() == "e":
        math.math5(Numer, Duner)
        num3 = math.math5(num3)
        den3 = math.math5(den3)

    elif menu.ask() == "F" or menu.ask() == "f":
        math.math6(Numer, Duner)
        num3 = math.math6(num3)
        den3 = math.math6(den3)

    math.reduce(num3, den3)

    print(num3, '/', den3)

main()

第一组 if 语句只覆盖大小写字母 a-f。

Answer 1

您多次致电menu.ask()。每次你把它写在那里，例如if menu.ask() == 'a' or menu.ask() == 'A'...，它将调用该函数（除非/直到它短路），该函数要求输入。而是调用一次并保存：

ask = menu.ask()
if ask == 'b' or ask == 'B'...
    ...
elif ask == 'a' or...
    ...

或使用in 运算符：

ask = menu.ask()
if ask in 'bcdeBCDE':
    ...
elif ask in 'aAfF':
    ...

有关更多输入验证策略，请参阅Asking the user for input until they give a valid response。