一、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。获取用户输入后，Python将其存储在一个变量中，以方便使用。
例如以下代码：
message=input("Please tell me something.\n")
print(message)
输出如下：
Please tell me something.
abc
abc
其中第一个abc为你的输入（可为任意值）
注意：使用input()时，Python将用户输入解读为字符串。若想输出数值，可通过int（）。
动手试一试7-1 – 7-3
#7-1
car=input("Which car do you want to rent?")
print("Let me see if I can find a "+car+"\n")
#7-2
number=input("How many people?")
if int(number)>8:
print("We don't have enough tables.")
else:
print("Welcome!")
print("\n")
#7-3
num=input("Please input a number:")
if int(num)%10:
print("no")
else:
print("yes")
输出：
Which car do you want to rent?bmw
Let me see if I can find a bmw
How many people?9
We don't have enough tables.
Please input a number:12
no
二、while循环
1.使用while循环
运行如下代码:
number=1
while number<=5:
print(number)
number+=1
输出如下：
1
2
3
4
5
2.break与continue语句
break语句为退出整个循环，执行下面的语句。
continue语句为退出该次循环，回到循环判定条件。
动手试一试 7-4 – 7-7
#7-4
pizza=input("Please input a kind of food or input 'quit':")
while pizza!='quit':
print("We will add "+pizza +" in your pizza")
pizza=input("Please input a kind of food or input 'quit':")
#7-5
while True:
age = int(input("How old are you? "))
if age < 3:
print("free")
elif age >= 3 and age < 12:
print("10 dollars")
elif age >= 12:
print("15 dollars")
#7-6 7-7
#略
输出如下：
Please input a kind of food or input 'quit':eggs
We will add eggs in your pizza
Please input a kind of food or input 'quit':meat
We will add meat in your pizza
Please input a kind of food or input 'quit':quit
How old are you? 2
free
How old are you? 5
10 dollars
How old are you? 15
15 dollars
三、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。
1.在列表之间移动元素
假设有一个列表，其中包含新注册但还未验证的网站用户；验证这些用户后，将其移入另一个已验证的用户列表中，代码如下：
unconfirmed_users=['zhansan','lisi','wangwu']
confirmed_users=[]
while unconfirmed_users:
current_user = unconfirmed_users.pop()
print("Verifying user:"+current_user)
confirmed_users.append(current_user)
print("\nThe following users have been confirmed:")
for confirmed_user in confirmed_users:
print(confirmed_user)
输出如下：
Verifying user:wangwu
Verifying user:lisi
Verifying user:zhansan
The following users have been confirmed:
wangwu
lisi
zhansan
2.删除包含特定值的所有列表元素
pets=['cat','dog','goldfish','cat','rabbit']
print(pets)
while 'cat' in pets:
pets.remove('cat')
print(pets)
输出如下：
['cat', 'dog', 'goldfish', 'cat', 'rabbit']
['dog', 'goldfish', 'rabbit']
3.使用用户输入来填充字典
responses = {}
active = True
while 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 resond?(y/n)")
if repeat == 'y':
continue
elif repeat == 'n':
break
print("\n--- Poll Results ---")
for name,response in responses.items():
print(name+" would like to climb "+response+".")
输出如下：
What is your name?liming
Which mountain would you like to climb someday?a
Would you like to let another person resond?(y/n)y
What is your name?zhanghua
Which mountain would you like to climb someday?b
Would you like to let another person resond?(y/n)n
--- Poll Results ---
liming would like to climb a.
zhanghua would like to climb b.
动手试一试 7-8 — 7-10
#7-8
sandwich_orders=["a","b","c"]
finished_sandwiches=[]
while sandwich_orders:
sandwich = sandwich_orders.pop()
finished_sandwiches.append(sandwich)
print("I made your "+sandwich+" sandwich.")
#7-9
sandwich_orders = ["a","pastrami","c","pastrami","pastrami","b"]
print("The pastrami was sold out.")
while "pastrami" in sandwich_orders:
sandwich_orders.remove("pastrami")
print(sandwich_orders)
#7-10
travel_places = {}
while True:
name = input("What is your name?")
travel_places[name] = input("Where do you want to travel?")
judge = input("Do you want to repeat?(y/n)")
if judge == 'y':
continue
elif judge == 'n':
break
for name,place in travel_places.items():
print(name + " want to travel to " +place+".")
输出如下：
I made your c sandwich.
I made your b sandwich.
I made your a sandwich.
The pastrami was sold out.
['a', 'c', 'b']
What is your name?Liming
Where do you want to travel?Pairs
Do you want to repeat?(y/n)y
What is your name?Zhangsan
Where do you want to travel?Beijing
Do you want to repeat?(y/n)n
Liming want to travel to Pairs.
Zhangsan want to travel to Beijing.