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【day 5】python编程：从入门到实践学习笔记-用户输入和while循环（末答案）

2018-03-17 12:24 1126 查看

第七章用户输入和while循环

函数input()

input()

：暂停程序，等待用户输入文本并把文本存储在指定变量中。并接受一个参数，即要向用户显示的提示或说明。

int()

：使用

input()

函数时，输入的文本会被当成字符串，所以可以用这个函数将其化为int型。

：求模运算符。讲两个数相除并返回余数。

下面举个例子：

message = input("Tell me your name:")
print(message)
message = input("Tell me your years:")
if int(message) >= 18:
print('wow')
print(int(message) % 6)

运行结果：
Tell me your name:mike
mike
Tell me your years:19
wow
1

while循环

循环简介

while循环不断运行，直到指定的条件不满足位置。例如：

current_number = 1
while current_number <= 5:
print(current_number)
current_number += 1

运行结果：
1
2
3
4
5

还可以让用户选择何时退出，只要把循环的条件由

current_number <= 5

改为

message != 'quit'

，然后在循环语句里面添加

message = input(prompt)

，即：

current_number = 1
while message != 'quit':
message = input('Enter 'quit' to end the program or go on:')
print(current_number)
current_number += 1

运行结果：
Enter 'quit' to end the program or go on:
1
Enter 'quit' to end the program or go on:
2
Enter 'quit' to end the program or go on:quit

这时候我们提示了一条消息：要么输入quit来结束程序，要么继续运行。当然我们还可以设置标志来决定循环的条件，比如利用布尔值

True

或者

False

。

退出循环

break

：不管条件测试结果如何，立即退出循环，不在运行循环中余下代码。

prompt = "\nPlease enter a city you have visited:"
prompt += "\n(Enter 'quit' when you are finished.) "
while True:
city = input(prompt)
if city == 'quit':
break

运行结果：
Please enter a city you have visited:
(Enter 'quit' when you are finished.) China
I'd love to go to China!

Please enter a city you have visited:
(Enter 'quit' when you are finished.) San Francisco
I'd love to go to San Francisco!

Please enter a city you have visited:
(Enter 'quit' when you are finished.) quit

continue

：跳出此次循环，即返回到循环开头，并判断循环条件是否满足来决定是否执行循环。

current_number = 0
while current_number < 10:
current_number += 1
if current_number % 2 == 0:
continue
print(current_number)

运行结果：
1
3
5
7
9

使用循环处理列表和字典

for循环中不应修改列表，因为for循环中修改列表之后，python的遍历会出现问题。而要想遍历列表并修改，可以用while循环。下面举几个例子。

在列表之间移动元素

#创建待验证用户列表和一个已验证用户列表
unconfirmed_ids = ['mike', 'lili', 'ace']
confirmed_ids = []
#验证每个用户并把其移动到已验证用户列表
while unconfirmed_ids:
current_id = unconfirmed_ids.pop()
print("Verifying id: " + current_id.title())
confirmed_ids.append(current_id)
#显示所有已验证id
print("\nThe following ids have been confirmed:")
for confirmed_id in confirmed_ids:
print(confirmed_id.title())

运行结果：
Ace
Lili
Mike

删除包含特定值的所有列表元素

nums = ['1', '3', '5', '1', '6', '1', '7']
print(nums)
while '1' in nums:
pets.remove('1')
print(nums)

运行结果：
['3', '5', '6', '7']

使用用户输入来填充字典

responses = {}
#设置一个标志ǈ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? ")

#将答卷存储在字典中
responses[name] = response

#看看是否有人要参与调查
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 + ".")

运行结果：
What is your name? Eric
Which mountain would you like to climb someday? Denali
Would you like to let another person respond? (yes/ no) yes

What is your name? Lynn
Which mountain would you like to climb someday? Devil's Thumb
Would you like to let another person respond? (yes/ no) no

--- Poll Results ---
Lynn would like to climb Devil's Thumb.
Eric would like to climb Denali.

第七章练习答案代码

链接: https://pan.baidu.com/s/16Laof481DMs8VhHABYENaQ 密码: eff2

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【day 5】python编程：从入门到实践学习笔记-用户输入和while循环（末答案）

第七章 用户输入和while循环

函数input()

while循环

使用循环处理列表和字典

第七章用户输入和while循环