一、input输入函数

input( ) 方法：获取用户的输入信息，使用函数input() 时，Python将用户输入解读为字符串。

如果想要将input输入的字符串转换成需要的变量类型（如整型int），则可以使用int（）函数进行类型转换。

实例

1. 让用户输入自己的年龄，并且判断是否为成年人（>=18岁）

age = input("Please input your age :")
age = int(age)
if age >= 18:
    print("You are an adult now!")
else:
     print("You need tu grow up!")

2. 让用户输入一个数，并指出该数是否是10的整数倍。

number = int(input("Please input an integer: "))
if number%10==0:
    print("This number is a multiple of ten.")
else:
    print("This number is not a multiple of ten.")

二、while循环

2.1 while结构

练习题

7-4
使用break关键词结束循环。

prompt = "Please enter the topping of pizza: "
prompt += "(Enter 'quit' when you are finished.)"
while True:
    topping = input(prompt)
    if topping == 'quit':
        print("exit")
        break
    else:
        print(f"We are gonna put {topping} into your pizza.")

7-5
使用flag标记结束循环。

flag = True
while flag:
    age = input("Input the age (Enter quit to end this program) : ")
    if age == 'quit':
        flag = False
    else:
        age = int(age)
        if age < 3:
            print("free.")
        elif age >= 3 and age <= 12:
            print("charge 10.")
        else:
            print("charge 15.")

2.2 使用while循环处理列表和字典

2.2.1 在列表之间移动元素

假设有一个列表包含新注册但还未验证的网站用户，验证这些用户后，将他们从原列表中删除，然后添加到另一个已验证用户列表中。

• 因为题目要求要将验证后的用户名称从原列表中删除，说明列表是需要动态变化的，所以不能使用for循环进行对原列表的遍历，可以使用while循环对列表进行判断，结束条件即为列表为空时。
• 在while循环中，使用pop方法把原有列表中的元素弹出，然后使用append方法添加进新列表中，当原列表中所有元素都被弹出时（列表为空），则结束循环。

unconfirmed_users = ['jack','alice','will','mary']
confirmed_users = []

while unconfirmed_users:
    current_user = unconfirmed_users.pop()
    print(f"Verifying user: {current_user.title()}")
    confirmed_users.append(current_user)

print("The following users have been confirmed: ")
for confirmed_user in confirmed_users:
    print(confirmed_user.title())

2.2.2 删除为特定值的多个列表元素

当列表中有多个相同的元素并且需要把他们都删除时，单独使用remove无法实现，因此使用while循环，当还有该元素在列表中时，就一直执行remove操作。

pets = ['dog', 'cat', 'dog', 'goldfish', 'cat', 'rabbit', 'cat']
print(pets)

while 'cat' in pets:
    pets.remove('cat')

print(pets)

2.2.3 使用用户输入来填充字典

创建一个调查程序，其中的循环每次执行时都提示输入用户的名字和年龄。将收集的数据存储在一个字典中。

• 使用flag标志进行循环是否结束的判断

responses = {}
flag = True
while flag:
    name = input("What's your name? ")
    age = int(input("How old are you? "))
    responses[name] = age

    repeat = input("Would you like to let another person respond? (yes/ no) ")
    if repeat=='no':
        flag=False

print("Results")
for name,age in responses.items():
    print(f"{name} is {age} years old.")

练习题

7-8

sandwich_orders=["Black Forest Ham","Chicken & Bacon Ranch Melt","Cold Cut Combo"
                 ,"Italian B.M.T.","Meatball Marinara","Oven Roasted Chicken","Veggie Delite"]
finished_snadwiches=[]

while sandwich_orders:
    sandwich_being_made = sandwich_orders.pop()
    print(f"I made your {sandwich_being_made} Sandwich.")
    finished_snadwiches.append(sandwich_being_made)

for finished_snadwich in finished_snadwiches:
    print(finished_snadwich)

7-9

print("Sorry, we have already sold all the pastrami!")
sandwich_orders=["Black Forest Ham","pastrami","Chicken & Bacon Ranch Melt",
                 "Cold Cut Combo","Italian B.M.T.","pastrami",
                 "Meatball Marinara","Oven Roasted Chicken",
                 "pastrami","Veggie Delite"]
print(sandwich_orders)
while 'pastrami' in sandwich_orders:
    sandwich_orders.remove('pastrami')

finished_snadwiches=[]

while sandwich_orders:
    sandwich_being_made = sandwich_orders.pop()
    print(f"I made your {sandwich_being_made} Sandwich.")
    finished_snadwiches.append(sandwich_being_made)

print(finished_snadwiches)

7-10

flag = True
results = {}
while flag:
    name = input("Please enter your name: (Enter exit to end this program.)")
    if name == 'exit':
        print("exit")
        flag = False
    else:
        place = input("If you could visit one place in the world, where would you go? ")
        results[name]=place

for name,place in results.items():
    print(f"{name.title()} wanna go {place.title()}!")