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while循环同列表和字典结合起来使用，可收集、存储组织大量输入，供以后查看和显示.
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，如何将他们移动另一个已验证用户列表中呢？一种办法就是使用while循环，在验证用户的同时将其从未验证用户列表中提取出来，将其加入另一个验证用户列表中. 代码类似如下：
unconfirmed_users = ["alice", "brian", "candace"]
confirmed_users = []
# 验证每个用户，直到没有未验证的用户为止
# 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)
# 显示所有已验证用户
print("\nThe following users have been confirmed: ")
for confirmed_user in confirmed_users:
print(confirmed_user.title())
"""
在 VS Code 输出结果：
---------------------
Verifying user: Candace
Verifying user: Brian
Verifying user: Alice
The following users have been confirmed:
Candace
Brian
Alice
---------------------
"""2 删除为特定值的所有列表元素
我们知道可以通过remove()来删除列表中的特定值. 如果列表中重复项出现一次，还好说，如果出现多次，如：一个宠物列表中，cat出现了3次，难道还一个一个手动删除？其实可以用while循环很好的解决这个问题：
pets = ["dog", "cat", "dog", "goldfish", "cat", "rabbit", "cat"]
while "cat" in pets:
pets.remove("cat")
print(pets)
"""
在 VS Code 输出结果：
---------------------
['dog', 'dog', 'goldfish', 'rabbit']
---------------------
"""3 使用用户输入来填充字典
可使用while循环提示用户输入任意多的信息. 下面创建一个调查程序，其中的循环每次执行时都提示被调查者的名字和回答. 我们将收集的数据存储一个字典中，以便将回答同被调查者关联起来：
reponses = {}
# 设置一个标志，指出调查是否继续
polling_active = True
while polling_active:
name = input("\nWhat is your name? ")
reponse = input("Which mountain would like to climb someday? ")
# 将回答存储在字典中
reponses[name] = reponse
repeat = input("Would you like to let another person respond? (yes/no) ")
if repeat.title() == "No":
polling_active = False
print("\n---Poll Results---")
for name, reponse in reponses.items():
print(f"{name.title()} would like to climb {reponse}.")
"""
在 VS Code 输出结果：
---------------------
What is your name? Eric
Which mountain would like to climb someday? Denali
Would you like to let another person respond? (yes/no) yes
What is your name? Lynn
Which mountain would 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.
---------------------
"""- 小练习
1) 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_sandwichs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，并将其移到列表finished_sandwichs中. 所有三明治都制作好后，打印一条消息，将这些三明治残出来：
sandwich_orders = ["tuna", "ham cheese", "chicken breast"]
finished_sandwichs = []
while sandwich_orders:
sandwich_order = sandwich_orders.pop()
print(f"I made your {sandwich_order.title()} sandwich.")
finished_sandwichs.append(sandwich_order)
print("\nThe following sandwich have been made: ")
for finished_sandwich in finished_sandwichs:
print(f"{finished_sandwich.title()}.")
"""
在 VS Code 输出结果：
---------------------
I made your Chicken Breast sandwich.
I made your Ham Cheese sandwich.
I made your Tuna sandwich.
The following sandwich have been made:
Chicken Breast.
Ham Cheese.
Tuna.
---------------------
"""2) 五香熏牛肉卖完了 在上面一个练习的基础上，在创建的列表sandwich_orders确保"pastrami"在其中至少出现三次，在程序的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_sandwichs未包含"pastrami".
sandwich_orders = ["tuna", "pastrami", "ham cheese","pastrami", "chicken breast", "pastrami"]
finished_sandwichs = []
print("Pastrami sold out!")
while "pastrami" in sandwich_orders:
sandwich_orders.remove("pastrami")
while sandwich_orders:
sandwich_order = sandwich_orders.pop()
print(f"I made your {sandwich_order.title()} sandwich.")
finished_sandwichs.append(sandwich_order)
print("\nThe following sandwich have been made: ")
for finished_sandwich in finished_sandwichs:
print(f"{finished_sandwich.title()}.")
"""
在 VS Code 输出结果：
---------------------
Pastrami sold out!
I made your Chicken Breast sandwich.
I made your Ham Cheese sandwich.
I made your Tuna sandwich.
The following sandwich have been made:
Chicken Breast.
Ham Cheese.
Tuna.
---------------------
"""3) 梦想的度假地 编写一个程序，调查用户梦想的度假胜地.
resorts = {}
active = True
while active:
name = input("\nWhat's your name? ")
resort = input("If you could visit one place in the world, where would you go? ")
resorts[name] = resort
repeat = input("Would you like to another person repond?(yes/no)")
if repeat.title() == "No":
active = False
print("\n--resorts--")
for name, resort in resorts.items():
print(f"{name.title()} want to visit {resort.title()}.")
"""
在 VS Code 输出结果：
---------------------
What's your name? john
If you could visit one place in the world, where would you go? beijing
Would you like to another person repond?(yes/no)yes
What's your name? pwg
If you could visit one place in the world, where would you go? shanghai
Would you like to another person repond?(yes/no)no
--resorts--
John want to visit Beijing.
Pwg want to visit Shanghai.
---------------------
"""