在Python中，else块可以有更多的if-elif-else块吗？

Question

电影票:电影院根据人的年龄收取不同的票价。如果一个人在3岁以下，门票是免费的；如果他在3岁到12岁之间，门票是10美元；如果他超过12岁，门票是15美元。写一个循环，你问用户他们的年龄，然后告诉他们电影票的价格。

我希望这个程序有退出的价值。我本可以使用0作为退出值，但我想使用' quit‘。

prompt = "What is your age? "
prompt += "\nEnter 'quit' to close program."

age = 0

while True:


     age = raw_input(prompt)
        if age == 'quit':
            break
        else:
            age = int(age)
            if age < 3:
                print("The movie ticket is FREE for you.")
            elif 3 <= age < 12:
                print("The movie ticket is $10 for you.")
            elif age >= 12:
                print("The movie ticker is $15 for you.")

Answer 1

我想指出的是，您不需要else子句。您可以在先前的缩进级别包括其余的条件条件，因为break将退出循环，而不是继续循环主体的其余部分。

而不是

    if age == 'quit':
        break
    else:
        age = int(age)

简单地说：

    if age == 'quit':
        break

    age = int(age)

如果不清楚这一点，这里是整个程序的变化：

prompt = "What is your age? "
prompt += "\nEnter 'quit' to close program."

while True:

    age = raw_input(prompt)
    if age == 'quit':
        break

    age = int(age)
    if age < 3:
        print("The movie ticket is FREE for you.")
    elif 3 <= age < 12:
        print("The movie ticket is $10 for you.")
    elif age >= 12:
        print("The movie ticker is $15 for you.")

我还删除了无用的赋值：age = 0，因为在读取该值之前，该值已被age = raw_input(prompt)替换。

Answer 2

是的，如果你喜欢，你可以嵌套if语句，但我总是尝试先找到一种更好的方法。在这种情况下，我们可以使用while语句的条件部分。

age = 0
while age != "quit":
    age = raw_input(prompt)
    age = int(age)
    if age < 3:
        print("The movie ticket is FREE for you.")
    elif 3 <= age < 12:
        print("The movie ticket is $10 for you.")
    elif age >= 12:
        print("The movie ticker is $15 for you.")

现在，只要age不等于"quit"，代码就会循环。

Answer 3

您可以使用try:通过输入其他值而不是整数来避免脚本崩溃。

prompt = "What is your age? [quit to Exit the program] : "
while True:
     age = raw_input(prompt)
     if age == 'quit':
        break
     try:
        age = int(age)
        if age < 3:
            print("The movie ticket is FREE for you.")
        elif 3 <= age < 12:
            print("The movie ticket is $10 for you.")
        elif age >= 12:
            print("The movie ticker is $15 for you.")
     except:
        print 'Invalid Age entered !!!'
        pass