1. input()函数
input（）函数可以在括号中写入提示，用户根据提示输入信息，并且将信息作为一个字符串，保存在变量中。
输入：
prompt='If you tell us who you are, we can personalize the messages you see.'
prompt+='\nWhat is your first name? ' #prompt第二种方法
first_name=input(prompt)
last_name=input('What is your last name? ') #prompt第一种方法
print('\nhello, '+first_name+' '+last_name+'!')
输出：
c:\py>input
If you tell us who you are, we can personalize the messages you see.
What is your first name? tao
What is your last name? ming
hello, tao ming!
2. int()函数
如果你要用户输入数字，并且要将其作为整型变量用来进行数字方面的处理，需要使用int()函数。
输入：
height=input('how old are you?')
height=int(height)
if height>=18:
print('you are old enogh')
else:
print('you are too young')
输出：
c:\py>int_input
how old are you?16
you are too young
c:\py>int_input
how old are you?19
you are old enogh
3. while循环
当while后面的值为true时，执行while下面缩进的语句。
输入：
prompt='\nTell me something,and I will repeat it back to you:'
prompt+="\nenter 'quit' to end the program.\n"
message="" #一开始为空字符串，但它依然为字符串，这样才能比较
while message != 'quit':
message = input(prompt)
if message != 'quit':
print(message)
输出：
c:\py>while
Tell me something,and I will repeat it back to you:
enter 'quit' to end the program.
we
we
Tell me something,and I will repeat it back to you:
enter 'quit' to end the program.
quit
4. 用Flag控制while循环
while Falg：那我们可以通过控制Flag的True或者Flase来控制程序流。
输入：
prompt='\nTell me something,and I will repeat it back to you:'
prompt+="\nenter 'quit' to end the program.\n"
active = True
while active:
message = input(prompt)
if message == 'quit':
active = False
else:
print(message)
输出：
c:\py>flag
Tell me something,and I will repeat it back to you:
enter 'quit' to end the program.
else
else
Tell me something,and I will repeat it back to you:
enter 'quit' to end the program.
quit
c:\py>
5. break语句
若在循环中遇到break语句，程序跳过剩余的循环语句，直接跳出循环。
输入：
prompt='\nTell me something,and I will repeat it back to you:'
prompt+="\nenter 'quit' to end the program.\n"
#和上一个程序比，因为有了break语句，判别是否跳出循环的任务就交给了if
while True:
message = input(prompt)
if message == 'quit':
break
else:
print(message)
输出:
Tell me something,and I will repeat it back to you:
enter 'quit' to end the program.
me
me
Tell me something,and I will repeat it back to you:
enter 'quit' to end the program.
quit
c:\py>
6. continue语句
在循环中，continue语句会跳过剩余的循环语句，回到循环的开头，重新开始循环。即跳过本次剩余的循环，直接开始下一个循环。
输入：
current_number=0
while current_number <= 10:
current_number+=1
if current_number%2==0:
continue
print(current_number)
输出：
c:\py>continue_
1
3
5
7
9
11
程序中，while循环的条件是current_number<=10,但当current_number=10时，符合条件，while又进行一次循环，使current_number+1后变成11输出，在检测发现11不再<=10,所以跳出循环。
7. 用while循环处理列表
(1) 将一个列表元素移到另一个列表
输入：
unconfirmed_users=['alice','kitty','john']
confirmed_users=[]
while unconfirmed_users:
current_user=unconfirmed_users.pop()
print("verifying user: "+current_user.title())
confirmed_users.append(current_user)
print('\nthe following users are confirmed: ')
for confirmed_user in confirmed_users:
print(confirmed_user.title()) #方法一定要带（）
输出:
c:\py>while_pop_append
verifying user: John
verifying user: Kitty
verifying user: Alice
the following users are confirmed:
John
Kitty
Alice
(2) 用while循环和.renmove()方法移除所有指定元素
.remove()方法只能移除移除第一个指定的元素，加上while循环，可以移除所有的指定元素。
输入：
pets=['dog','cat','goldfish','cat','rabbit','cat']
print(pets)
while 'cat' in pets:
pets.remove('cat')
print(pets)
输出:
c:\py>while_remove
['dog', 'cat', 'goldfish', 'cat', 'rabbit', 'cat']
['dog', 'goldfish', 'rabbit']
(3) 用while循环填充字典
输入：
prompt_1='\nwho are you?'
prompt_2='what food do you like best?'
responses={}
while True:
name=input(prompt_1)
food=input(prompt_2)
responses[name]=food #添加键值对只需一条语句即可
answer=input('would you like to let another person respond?(yes/no)')
if answer=='no':
break
print('\n this is poll results\n')
print(responses)
输出：
c:\py>while_dic
who are you?mike
what food do you like best?pear
would you like to let another person respond?(yes/no)yes
who are you?jack
what food do you like best?apple
would you like to let another person respond?(yes/no)yes
who are you?john
what food do you like best?strawberry
would you like to let another person respond?(yes/no)no
this is poll results
{'mike': 'pear', 'jack': 'apple', 'john': 'strawberry'}
