一.input()函数
1）input()
input接受一个参数，向用户显示的提示说明，输入存储在变量中
eg1：
message = input("Tell me something, and I will repeat it back to you: ")
print(message)
输出
Tell me something, and I will repeat it back to you: hello world
hello world
eg2：
name = input("Please inter your name: ")
print("Hello, " + name + "!")
输出
Please inter your name: Eric
Hello, Eric!
eg3：
prompt = "If you tell us who you are, we can peisonalize the message you see"
prompt += "\nWhat is your first name?"
name = input(prompt)
print("\nHello " + name + "!")
输出
If you tell us who you are, we can peisonalize the message you see
What is your first name?Eric
Hello Eric!
2）int()获取数值输入
使用函数input()，Python将用户的输入解读为字符串，如果要获得整数，就需要调用int函数
eg1：
>>> age = input("How old are you? ")
How old are you? 21
>>> age>=18
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: '>=' not supported between instances of 'str' and 'int'
>>>
这里的21是作为字符串str的类型，需要做整数处理的时候就要用到int()函数
>>> age = input("How old are you? ")
How old are you? 21
>>> age = int(age)
>>> age>=18
True
eg2：
height = input("How tall are you, in inches? ")
height = int(height)
if height >= 36:
print("\nYou're tall enough ro ride")
else:
print("\nYou'll be able to ride when you're a little older")
输出
How tall are you, in inches? 71
You're tall enough ro ride
3）取模运算
**%**用法同C
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number = input("Enter a number, and I'll tell you if it is even or odd: ")
number = int(number)
if number%2 == 0:
print("\nThe number " + str(number) + " is even.")
else:
print("\nThe number " + str(number) + " is odd.")
输出
Enter a number, and I'll tell you if it is even or odd: 42
The number 42 is even.
二.while循环
1）while循环
eg：
current_number = 1
while current_number < 5:
print(current_number)
current_number += 1 #这里不能是current_number++
输出
1
2
3
4
2）让用户选择合适退出
prompt = "\nTell me something, and I will repeat it back to you: "
prompt += "\nEnter 'quit' to end this program."
message=""
while message != 'quit':
message = input(prompt)
print(message)
输出
Tell me something, and I will repeat it back to you:
Enter 'quit' to end this program.hello everyone
hello everyone
Tell me something, and I will repeat it back to you:
Enter 'quit' to end this program.hello again
hello again
Tell me something, and I will repeat it back to you:
Enter 'quit' to end this program.quit
quit
3）使用标志
定义bool类型变量决定while循环进行 flag
eg：
prompt = "\nTell me something, and I will repeat it back to you: "
prompt += "\nEnter 'quit' to end this program."
active = True
while active:
message = input(prompt)
if message == 'quit':
active = False
else:
print(message)
输出
Tell me something, and I will repeat it back to you:
Enter 'quit' to end this program.hello world
hello world
Tell me something, and I will repeat it back to you:
Enter 'quit' to end this program.quit
4）使用break退出循环
eg:
prompt = "\nPlease enter the name of a city you have visited"
prompt += "\n(Enter 'quit when you are finished')"
while True:
city = input(prompt)
if city == 'quit':
break
else:
print("I'd like love to go to " + city.title() + "!")
输出
Please enter the name of a city you have visited
(Enter 'quit when you are finished')New York
I'd like love to go to New York!
Please enter the name of a city you have visited
(Enter 'quit when you are finished')San Francisco
I'd like love to go to San Francisco!
Please enter the name of a city you have visited
(Enter 'quit when you are finished')quit
5）continue
用法同 C
eg：
current_number = 0
while current_number < 10:
current_number += 1
if current_number % 2 == 0:
continue
print(current_number)
输出
1
3
5
7
9
无限循环时使用ctrl+C结束终端窗口
三.使用while循环处理列表和字典
1）在列表之间移动元素
#创建待验证用户列表和存储已验证用户空间列表
unconfirmed_users = ['alice', 'brian', 'candace']
confirmed_users = []
#验证每个用户，直到没有未验证用户为止，将每个经过验证的列表都移到已验证的用户列表中
while unconfirmed_users:#如果列表中没有元素，则返回false
current_users = unconfirmed_users.pop()
print("Verifying user: " + current_users.title())
confirmed_users.append(current_users)
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
2）删除包含特定值的所有列表元素
eg：
pets = ['dog', 'cat', 'dog', 'goldfish', 'cat', 'rabbit', 'cat']
print(pets)
while 'cat' in pets:
pets.remove('cat')#remove会删除pets中第一个值为cat的元素
print(pets)
输出
['dog', 'cat', 'dog', 'goldfish', 'cat', 'rabbit', 'cat']
['dog', 'dog', 'goldfish', 'rabbit']
3）使用用户输入来填充字典
eg：
responses = {}
polling_active = True
while polling_active:
name = input("\nWhat is your name?")
response = input("Which mountain would you like to climb somedays?")
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 wo climb " + response + ".")
输出：
What is your name?Eric
Which mountain would you like to climb somedays?Denali
Would you like to let another person respond? (yes/no)yes
What is your name?Lynn
Which mountain would you like to climb somedays?Devil's Thumb
Would you like to let another person respond? (yes/no)no
--- Poll Results ---
namewould like wo climb Denali.
namewould like wo climb Devil's Thumb.
