我的“如果声明”不会

Question

def main():
    while True:
        operation = raw_input('Choose an operation: ')

        if operation == 1:
            number_1 = int(raw_input("What is the first number you want to subtract? "))
            number_2 = int(raw_input("What do you want to subtract from it? "))
            sum = number_1 - number_2
            print('The answer is...')
            print(sum)
            break

        if operation == 2:
            number_1 = int(raw_input("What is the first number you want to subtract? "))
            number_2 = int(raw_input("What do you want to subtract from it? "))
            sum = number_1 - number_2
            print('The answer is...')
            print(sum)
            break

        if operation == 3:
            number_1 = int(raw_input("What is the first number you want to subtract? "))
            number_2 = int(raw_input("What do you want to subtract from it? "))
            sum = number_1 - number_2
            print('The answer is...')
            print(sum)
            break

        if operation == 4:
            number_1 = int(raw_input("What is the first number you want to subtract? "))
            number_2 = int(raw_input("What do you want to subtract from it? "))
            sum = number_1 - number_2
            print('The answer is...')
            print(sum)
            break

        else:
            print('Invalid operation')
            break
main()

当我尝试输入一个数字时，它无法识别它并打印出无效的操作

Answer 1

必须比较字符串：

if operation == "1":

Answer 2

必须使用^{}将输入转换为整数：

operation = int(raw_input('Choose an operation: '))

Answer 3

将if语句设置为：

if int(operation) == 1

或者

if operation == str(1)