《Python编程：从入门到实践（第二版）》自学笔记（十二）

利用while循环处理列表

在Python中，接触最频繁的，无非是：变量、、循环、列表、元素、元组、字典、函数、方法、类…..尽管有些还没接触，很快就会碰到

while对列表的处理，通常发生在列表与列表之间，从一个列表到另外一个列表，来回变动

# 首先，创建一个待验证用户列表 
# 和一个用于存储已验证用户的空列表
unconfirmed_users = ['alice', 'brian', 'candace'] 
confirmed_users = [] 

# 验证每个用户，直到没有未验证用户为止
# 将每个经过验证的用户都移到已验证用户列表中
while unconfirmed_users: 
	current_user = unconfirmed_users.pop() 
	print(f"Verifying user: {current_user.title()}") 			
	confirmed_users.append(current_user) 

# 显示所有已验证的用户
print("\nThe following users have been confirmed:") 
for confirmed_user in confirmed_users: 
	print(confirmed_user.title())
输出：
Verifying user: Candace 
Verifying user: Brian 
Verifying user: Alice 

The following users have been confirmed: 
Candace 
Brian 
Alice

之前在刚开始接触列表时，曾经提及到删除列表中的某个元素，使用的是方法.remove( )，当但是也提醒的是：它只删除第一个指定的值，如果要删除的值可能在列表中出现多次，就需要使用循环来确保将每个值都删除

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

利用while循环处理字典

对于利用while循环来处理列表，不深究，不细究。因为对于字典来讲，前面说过它里面的数据都是以键值对的形式存在的，那么对于利用while循环，需保存的数据就会渐渐增加，越来越多后容易造成代码的复杂，就跟嵌套中的第三种，字典字典一样

responses = {}

# 设置一个标志，指出调查是否继续
polling_active = True

while polling_active:
# 提示输入被调查者的名字和回答
	name = input("\nWhat is your name? ")
	response = input("Which mountain would you like to climb someday? ")
# 将回答存储在字典中
	responses[name] = response
# 看看是否还有人要参与调查
	repeat = input("Would you like to let another person respond? (yes/ no)
	if repeat == 'no':
		polling_active = False
# 调查结束，显示结果
print("\n--- Poll Results ---")
for name, response in responses.items():
	print(f"{name} would like to climb {response}.")
	
输出：
What is your name? 
Eric Which mountain would you like to climb someday? 
Denali Would you like to let another person respond? (yes/ no) yes 

What is your name?
Lynn Which mountain would you like to climb someday?
Devil's Thumb Would you like to let another person respond? (yes/ no) no 

--- Poll Results --- 
Eric would like to climb Denali. 
Lynn would like to climb Devil's Thumb.

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