Question

我想选择用户输入的首字母并将其用于循环决策。一个简单的例子：

cat

程序应将“是”检测为“ Y”，将“否”检测为“ N”。

Answer 1

要选择第一个字母，只需在输入后添加[0]。 [0]是字符串切片-在这里它仅提取字符串的第一个字符。还要注意，所有以'Y'开头的输入都将被视为“是”输出，而所有以'N'开头的输入都将被视为“否”输出。

play_again = input("Do you want to play again? (y/n)").lower()
# Simply add [0]. But that does not work for empty strings.
if len(play_again) > 0) 
    play_again = play_again[0]

请注意，如果您提供的输入为空，则该方法将不起作用-否则将导致回溯声明IndexError: string index out of range。这就是为什么要有一个if语句的原因。

示例：

Do you want to play again? (y/n)YES
y

Do you want to play again? (y/n)no
n

Do you want to play again? (y/n)OMG
o

Do you want to play again? (y/n)yakety yak
y

Do you want to play again? (y/n)
#Empty String

Answer 2

play_again = input("Do you want to play again? (y/n)").lower()

if play_again in ['yes', 'no', 'y', 'n']:
    play_again = play_again[0]

    if play_again == 'y':
        # do something

    else:
        # do something else

Answer 3

字符串索引类似于Python中的列表索引。因此，您可以直接索引第0个元素：

play_again = input('Do you want to play again? (y/n)')[0].lower()

例如：

Do you want to play again? (y/n)Yes

print(play_again)

'y'

Answer 4

play_again = input("Do you want to play again? (y/n)").lower()
first_letter=play_again[0]
#or
play_again = input("Do you want to play again? (y/n)").lower()[0]

Answer 5

我认为这正是您想要的：

<html>
<head>
<script type="text/javascript" src="https://platform.linkedin.com/in.js">  
api_key: [MY KEY] //Client ID  
onLoad: OnLinkedInFrameworkLoad //Method that will be called on page load  
authorize: true  
</script>  
</head>
<script type="text/javascript">  
function OnLinkedInFrameworkLoad() {  
    console.log('OnLinkedInFrameworkLoad');
    IN.Event.on(IN, "auth", OnLinkedInAuth);  
}  

function OnLinkedInAuth() {  
    console.log('OnLinkedInAuth');
    IN.API.Profile("me").result(ShowProfileData);  
}  

function ShowProfileData(profiles) {  
    console.log('ShowProfileData' + profiles);
    var member = profiles.values[0];  
    var id = member.id;  
    var firstName = member.firstName;  
    var lastName = member.lastName;  
    var photo = member.pictureUrl;  
    var headline = member.headline;  
    //use information captured above  
    var stringToBind = "<p>First Name: " + firstName + " <p/><p> Last Name: " 
+ lastName + "<p/><p>User ID: " + id + " and Head Line Provided: " + headline 
+ "<p/>"  
    document.getElementById('profiles').innerHTML = stringToBind;  
}  
</script>

<body>
<div id="profiles"></div>
</body>
</html>

说明：

play_again = input('Do you want to play again? (y/n)')[0].lower() while(play_again=='y'): # Do something play_again = input('Do you want to play again? (y/n)')[0].lower()从输入字符串中提取第一个字母，[0]会将字符标准化为小写，例如。 Y 或 y 到 y ， N 或 n 到 n < / strong>。

如果用户输入的字符串以 Y 或 y 开头，则.lower()循环触发器是第一次，并一直循环直到重复如此。中断条件是输入字符串不以 Y 或 y 开头。

从用户输入中选择第一个字母

5 个答案: