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.