一、用户输入

  1. 函数 .input() ：
    1. msg = input("Tell me something, and I will repeat it back to you: ")
    2. print(msg)
    :::tips 函数input()接受一个参数；在这个示例中，python运行第一行代码时，用户将看到提示：
    Tell me something, and I will repeat it back to you:
    程序等待用户输入，并在用户按回车键后继续运行。
    输入存储在变量msg中，接下来的print（msg）将输入输出。 :::

当必要的提示不止一行时，我们可以：

#先将部分提示存入一个变量，再使用+=运算符接上剩余的提示
prompt = "If you tell us who you are, we can personalize the messages you see."
prompt += "\nWhat is your first name? "

name = input(prompt)
print("\nHello, " + name + "!")

:::tips output：
If you tell us who you are, we can personalize the messages you see.
What is your first name? Ming

Hello, Ming! :::

  1. 使用 int() 来获取数值输入：
    input会将输入理解为字符串，我们需要int来转换。将数值用于计算和比较前，务必将其转化为数值表示，避免不必要的错误。 ```python height = input(“How tall are you, in inches? “) height = int(height) #转化为数值

if height >= 36: print(“\nYou’re tall enough to ride!”) else: print(“\nYou’ll be able to ride when you’re a little older.”)


3. 求模运算符：% （**同c/c++**）<br />**python 2.7 中应使用: raw_input()来获取输入。**

---

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## 二、while循环
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#### 1、简述：
```python
prompt = "\nTell me something, and I will repeat it back to you:"
prompt += "\nEnter 'quit' to end the program. "

active = True #随便定义的一个标志变量
while active: #while的用法与c/c++类似，区别是不用括号
    message = input(prompt)

    if message == 'quit':
        active = False
    else:
        print(message)

break/continue在python中的用法与c/c++中相同。

2、用while循环来处理列表和字典：

  1. 在列表间移动元素： ```python

    首先，创建一个待验证用户列表

    和一个用于存储已验证用户的空列表

    unconfirmed_users = [‘alice’, ‘brian’, ‘candace’] confirmed_users = []

验证每个用户，直到没有未验证用户为止

将每个经过验证的用户都移动到已验证用户列表中

while unconfirmed_users: current_user = unconfirmed_users.pop()

print("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())

:::tips
output：<br />Verifying user: Candace<br />Verifying user: Brian<br />Verifying user: Alice

The following users have been confirmed:<br />Candace<br />Brian<br />Alice
:::

2. **删除包含特定值的所有列表元素**：
```python
pets = ['dog', 'cat', 'dog', 'goldfish', 'cat', 'rabbit', 'cat']
print(pets)

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

print(pets)

:::tips output：
[‘dog’, ‘cat’, ‘dog’, ‘goldfish’, ‘cat’, ‘rabbit’, ‘cat’]
[‘dog’, ‘dog’, ‘goldfish’, ‘rabbit’] :::

  1. 使用用户输入来充填字典： ```python responses = {}

设置一个标志，指出调查是否继续

polling_active = True

while polling_active:

# 提示输入被调查者的名字和回答
name = input("\nWhat is your name? ")
response = input("Which mountain would you like to climb someday? ")

# 将答案存储在字典中
responses[name] = response

# 看看是否还有人要参与调查
repeat = input("Would you like to let another person respond? (yes/ no) ")
if repeat == 'no':
    polling_active = False

调查结束，显示结果

print(“\n—- Poll Results —-“) for name, response in responses.items(): print(name + “ would like to climb “ + response + “.”) ``` :::tips output：
What is your name? 小明
Which mountain would you like to climb someday? 珠穆朗玛峰
Would you like to let another person respond? (yes/ no) yes

What is your name? 不告诉你
Which mountain would you like to climb someday? 也不告诉你
Would you like to let another person respond? (yes/ no) no

—- Poll Results —-
小明 would like to climb 珠穆朗玛峰.
不告诉你 would like to climb 也不告诉你. :::