用户输入和while 循环

函数 input() 的工作原理
"""
函数input() 让程序暂停运行，等待用户输入一些文本。
使用函数input() 时，Python将用户输入解读为字符串。
"""
message= input("Tell me something, and I will repeat it back to you:")#2
print(message)

name = input("Please enter your name: ")
print(f"\nHello, {name}!")

prompt = "If you tell us who you are, we can personalize the messages you see."
prompt += "\nWhat is your first name? "
name = input(prompt)
print(f"\nHello, {name}!")

age = input("How old are you? ")#3
age=int(age)
if age >=18:
    print(age)

'''
Tell me something, and I will repeat it back to you:ad
ad
Please enter your name: yi

Hello, yi!
If you tell us who you are, we can personalize the messages you see.
What is your first name? chen

Hello, chen!
How old are you? 15'''

---

while 循环简介

"""
要立即退出while 循环，不再运行循环中余下的代码，也不管条件测试的结果如何，可使用break 语句。
要返回循环开头，并根据条件测试结果决定是否继续执行循环，可使用continue语句，它不像break 语句那样不再执行余下的代码并退出整个循环。
"""
prompt = "\nPlease enter the name of a city you have visited:"
prompt += "\n(Enter 'quit' when you are finished.) "
while True:
      city = input(prompt)
      if city == 'quit':
          break
      else:
          print(f"I'd love to go to {city.title()}!")

current_number = 0
while current_number < 10:
        current_number += 1
        if current_number % 2 == 0:
             continue
        print(current_number)
'''
Please enter the name of a city you have visited:
(Enter 'quit' when you are finished.) as
I'd love to go to As!

Please enter the name of a city you have visited:
(Enter 'quit' when you are finished.) quit
1
3
5
7
9
'''

---

"""
定义一个变量，用于判断整个程序是否处于活动状态。这个变量称为标志（flag），充当程序的交通信号灯。可以让程序在标志为True 时继续运行，并在任何事件导致标志的值为False 时让程序停止运行。
"""
current_number = 1
while current_number <= 5:
    print(current_number)
    current_number += 1

prompt = "\nTell me something, and I will repeat it back to you:"
prompt += "\nEnter 'quit' to end the program. "

active = True
while active:
    message = input(prompt)
    if message == 'quit':
         active = False
    else:
         print(message)
'''
1
2
3
4
5

Tell me something, and I will repeat it back to you:
Enter 'quit' to end the program. 1
1

Tell me something, and I will repeat it back to you:
Enter 'quit' to end the program. quit
'''

---

使用 while 循环处理列表和字典

"""
在列表之间移动元素
删除为特定值的所有列表元素
使用用户输入来填充字典
"""

unconfirmed_users = ['alice', 'brian', 'candace']
confirmed_users = []

while unconfirmed_users:
    current_user = unconfirmed_users.pop()
    print(f"Verifying user: {current_user.title()}")
    confirmed_users.append(current_user)
print("\nThe following users have been confirmed:")
for confirmed_user in confirmed_users:
      print(confirmed_user.title())

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

responses = {}
polling_active = True
while polling_active:
    name = input("\nWhat is your name? ")
    response = input("Which mountain would you like to climb someday? ")
    responses[name] = response
    repeat = input("Would you like to let another person respond? (yes/ no) ")
    if repeat == 'no':
        polling_active = False
print("\n--- Poll Results ---")
for name, response in responses.items():
    print(f"{name} would like to climb {response}.")
'''
Verifying user: Candace
Verifying user: Brian
Verifying user: Alice

The following users have been confirmed:
Candace
Brian
Alice
['dog', 'cat', 'dog', 'goldfish', 'cat', 'rabbit', 'cat']
['dog', 'dog', 'goldfish', 'rabbit']

What is your name? chen
Which mountain would you like to climb someday? chen
Would you like to let another person respond? (yes/ no) no

--- Poll Results ---
chen would like to climb chen.'''