7.3 使用while循环来处理列表和字典

for循环是一种遍历列表的有效方式，但在for循环中不应修改列表，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。

7.3.1 在列表之间移动元素

confirmed_users.py

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

while unconfirmed_users:
	current_users = unconfirmed_users.pop()
	
	print("Verifying user: " + current_user.title())
	confirmed_users.append(current_user)

print("\nThe following uses have been confirmed:")
for confirmed_user in confirmed_users:
	print(confirmed_user.title())

7.3.2 删除包含特定值的所有列表元素

pets.py

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

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

print(pets)

7.3.3 使用用户输入来填充字典

moutain_poll.py

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(name + " would like to climb " + response + ".")