Python编程-第七章-用户输入和while 循环

参考文章：
第 7 章 用户输入和while 循环

1. input（） 工作原理

函数input() 让程序暂停运行，等待用户输入一些文本。获取用户输入后，Python将其赋给一个变量，以方便你使用。例如，下面的程序让用户输入一些文本，再将这些文本呈现给用户：

1.1. 一个简单的input 输入

name =input("Please enter your name:")
print(f"\nHellp,{name}!")
# 增加更多提示信息。
prompt = "If you tell us who you ar ,we can persionalize the message you seee."
prompt += "\nWhat is your first name? "
name =input(prompt)
print(f"\nHellp,{name}!")

在第二行中，运算符+= 在前面赋给变量prompt 的字符串末尾附加一个字符串。

1.2. 将字符串转换为数字

age = input("How old are you? ")
age = int(age)
if age >= 18:
    print(f"True")
else:
    print(f"Fasle")
# 判断是否能够做过山车
height = input("How tall are you ,in cm?")
height = int(height)
if height >= 48:
    print("\n You're tall engough to ride!")
else:
    print(f"\n You'll be able to ride when you're a little older.")

2. 求模（求余数）

# 求偶数还是奇数
number = input("Enter a number ,and I'll tell you if it's even or odd:")
number = int (number)
if number % 2 == 0:
    print(f"\nThe numbder {number} is even.")
else:
    print(f"\nThe number {number} is odd.")

2.1. 练习题

练习7-1：汽车租赁 编写一个程序，询问用户要租赁什么样的汽车，并打印一条消息，下面是一个例子。

car = input("你想要什么汽车?")
print(f"\nLet me see if I can find you a {car}.")

练习7-2：餐馆订位 编写一个程序，询问用户有多少人用餐。如果超过8位，就打印一条消息，指出没有空桌；否则指出有空桌

user_number = input("有多少用户进行用餐？")
user_number = int(user_number)
if user_number > 8:
    print(f"没有空桌。")
else:
    print(f"有空桌。")

练习7-3：10的整数倍 让用户输入一个数，并指出该数是否是10的整数倍。

user_number = input("让我来告诉你此数是否是10 的整数倍。")
user_number = int(user_number)
if user_number % 10 == 0:
    print(f"是10 的整数倍。")
else:
    print(f"不是10 的整数倍。")

3. while 循环简介

for 循环用于针对集合中的每个元素都执行一个代码块，而while 循环则不断运行，直到指定的条件不满足为止

current_number = 1
while current_number <=5:
    print(current_number)
    current_number +=1

3.1. 用户输入控制循环条件

prompt = "\nTel me sometion, and I will repeat it back to you:"
prompt += "\nEnter 'quit' to end the program."
message =""
while message != 'quit':
    message = input(prompt)
    if message != 'quit':
        print(message)
# 使用标记进行循环条件的判断。
prompt = "\nTel me sometion, and I will repeat it back to you:"
prompt += "\nEnter 'quit' to end the program."
acitive = True

while acitive:
    message = input(prompt)
    if message == 'quit':
        acitive = False
    else:
        print(message)
# break 控制循环
while True:
    city = input(prompt)
    if city== 'quit':
        break
    else:
        print(city)
# 使用continue 控制循环。打印无法被 2 整除的数字。
current_number = 0
while current_number < 10:
    current_number +=1
    if current_number % 2 == 0:
        continue
    print(current_number)

3.2. 练习题

练习7-4：比萨配料 编写一个循环，提示用户输入一系列比萨配料，并在用户输入'quit' 时结束循环。每当用户输入一种配料后，都打印一条消息，指出我们会在比萨中添加这种配料

pizza=[]
acitive = True
prompt = "\nPlease add the required ingredients:"
prompt += "\nplease enter quit exit the program."
while acitive:
    burden=input(prompt)
    if burden == 'quit':
        acitive = False
    else:
        pizza.append(burden)
        print(pizza)

2334

练习7-5：电影票 有家电影院根据观众的年龄收取不同的票价：不到3岁的观众免费；3～12岁的观众收费10美元；超过12岁的观众收费15美元。请编写一个循环，在其中询问用户的年龄，并指出其票价。

while True:
    age = input("Please enter your age:")
    age = int(age)
    if age < 3:
        price = 0
        print(f"your fare is {price}")
    elif age >=3 and age <=12:
        price = 10
        print(f"your fare is {price}")
    elif age >12 :
        price = 20
        print(f"your fare is {price}")
    elif age == 'quit':
        break

4. 使用while 处理列表和字典

for 循环是一种遍历列表的有效方式，但不应在for 循环中修改列表，否则将导致Python难以跟踪其中的元素。要在遍历列表的同时对其进行修改，可使用while 循环。通过将while 循环同列表和字典结合起来使用，可收集、存储并组织大量输入，供以后查看和显示。

4.1. 在列表中移动元素

UNAUTHENTICATED_USER = ['alice','brian','candace']
confirmed_users = []
while UNAUTHENTICATED_USER:
    current_user = UNAUTHENTICATED_USER.pop()
    # pop is to remove the element from the end of the list each time and assign it to the current_user variable.
    print(f"Verifying user:{current_user.title()}")
    confirmed_users.append(current_user)
    # show all authenticated users
print("\nThe following users have been confirmed:")
for confirmed_user in confirmed_users:
    print(confirmed_user.title())

4.2. 删除为特定值的所有列表元素

pets = ['dog','cat','goldfish','cat','rabbit','cat']
print(pets)
while 'cat' in pets:
    pets.remove('cat')
    print(pets)

4.3. 使用用户输入来填充字典

responses = {}
polling_active = True
while polling_active:
    # Prompt for the respondent's name
    name=input("\nWhat is your name? ")
    response =input("Which mountain would you like to climb someday? ")
    # Store the answer in a dictionary.
    responses[name] = response
    # See if anyone else wants to take the survey.
    repeat = input("Would you like to let another persion respond? (yes/no)")
    if repeat == 'no':
        polling_active = False

    # The survey is over and the results are displayed
print("\n--- Poll Results ---")
for name,response in responses.items():
    print(f"{name} would like to climb {response}.")

4.4. 练习题

练习7-8：熟食店 创建一个名为sandwich_orders 的列表，在其中包含各种三明治的名字，再创建一个名为finished_sandwiches 的空列表。遍历列表sandwich_orders ，对于其中的每种三明治，都打印一条消息，如Imade your tuna sandwich ，并将其移到列表finished_sandwiches中。所有三明治都制作好后，打印一条消息，将这些三明治列出来

sandwich_orders =['alice','mawe','tage']
finished_sandwich =[]
while sandwich_orders:
    current_sanwich = sandwich_orders.pop()
    finished_sandwich.append(current_sanwich)
    print(f"I made you {current_sanwich}.")
print(f"I finnished all sandwich{finished_sandwich}")

练习7-9：五香烟熏牛肉卖完了 使用为完成练习7-8而创建的列表sandwich_orders ，并确保'pastrami' 在其中至少出现了三次。在程序开头附近添加这样的代码：打印一条消息，指出熟食店的五香烟熏牛肉（pastrami）卖完了；再使用一个while 循环将列表sandwich_orders 中的'pastrami' 都删除。确认最终的列表finished_sandwiches 未包含'pastrami'

sandwich_orders =['alice','mawe','pastrami','lili','pastrami','mato','pastrami']
print("All pastrami is sold out!")
while 'pastrami' in sandwich_orders:
    sandwich_orders.remove('pastrami')
print(sandwich_orders)

练习7-10：梦想的度假胜地 编写一个程序，调查用户梦想的度假胜地。使用类似于下面的提示，并编写一个打印调查结果的代码块。

responses = {}
polling_active = True
while polling_active:
    # Prompt for the respondent's name
    name=input("\nWhat is your name? ")
    response =input("Your dream vacation spot?")
    # Store the answer in a dictionary.
    responses[name] = response
    # See if anyone else wants to take the survey.
    repeat = input("Would you like to let another vaction? (yes/no)")
    if repeat == 'no':
        polling_active = False

    # The survey is over and the results are displayed
print("\n--- Poll Results ---")
for name,response in responses.items():
    print(f"{name} would like to vaction {response}.")