如何将字符串的首字母大写

huangapple go评论94阅读模式
英文:

How to capitalize the first letter of a string

问题

我有一个像这样的字符串:

var sentence string = "the biggest ocean is the Pacific ocean"

我想要能够将输入字符串中的第一个字母t大写,使得字符串变为:

"The biggest ocean is the Pacific ocean"

在Go语言中如何实现这个功能?

我尝试使用strings.Titlestrings.ToTitle,但它们并不符合我的要求。

英文:

I have a string like this

var sentence string = "the biggest ocean is the Pacific ocean"

I want to be able to capitalize the first letter t in the input string, so that the string becomes

"The biggest ocean is the Pacific ocean"

How to do that in Go?

I have tried using strings.Title and strings.ToTitle however they don't do what I want.

答案1

得分: 5

假设您的输入字符串是有效的UTF-8编码,这个线程(Golang - ToUpper() on a single byte?)非常接近,尽管不完全是一个完美的重复。我们可以在此基础上构建一个可接受的解决方案,使用unicode.ToUpper将字符串的第一个rune转换为大写。

r := []rune(s)
r[0] = unicode.ToUpper(r[0])
s := string(r)

或者使用一个“巧妙”的一行代码:

s := string(append([]rune{unicode.ToUpper(r[0])}, r[1:]...))

与字符串不同,rune切片是可变的,因此您可以用ToUpper替换第一个rune,它将处理具有大写形式的非ASCII和/或多字节代码点(例如俄语),并保持不变那些没有大写形式的代码点(例如亚洲文字)。

**注意:**大写形式和标题形式之间有区别,这在这里有简单的解释。简而言之,像DŽ这样的双字母字符在标题形式(Dž,只有第一个字母大写)和大写形式(DŽ,两个字母都大写)之间是不同的。如果您确实需要标题形式,请使用unicode.ToTitle

**注意2:**在string[]rune之间进行转换涉及到复制,因为您从一个不可变的字符串中获得了一个可变的切片。如果您希望在性能敏感的代码中使用它,请对您的应用程序进行性能分析。

Playground: https://go.dev/play/p/HpCBM7cRflZ


如果您有一个较大的输入字符串,完全转换为rune切片可能会变得太昂贵,您可以通过使用有限的strings.SplitN来解决这个问题,从而仅提取文本的第一个单词并在转换中仅使用该单词:

sep := " "
ss := strings.SplitN(s, sep, 2)

r := []rune(ss[0])
r[0] = unicode.ToUpper(r[0])

s = string(r) + sep + ss[1]

使用一个约30K的输入字符串进行基准测试显示出显著的差异:

go test -v -bench=. -benchmem
goos: darwin
goarch: arm64
pkg: example.com
BenchmarkRuneConv-10    	    6376	    183691 ns/op	  258049 B/op	       3 allocs/op
BenchmarkSplitN-10      	 1709989	       706.1 ns/op	    4152 B/op	       3 allocs/op
PASS
ok  	example.com	3.477s
英文:

Assuming that your input string is valid UTF-8, this thread (Golang - ToUpper() on a single byte?) is close enough, though not quite a perfect duplicate. We can build on that to come to an acceptable solution using unicode.ToUpper on the first rune of the string.

    r := []rune(s)
	r[0] = unicode.ToUpper(r[0])
	s := string(r)

Or with a "clever" one-liner:

    s := string(append([]rune{unicode.ToUpper(r[0])}, r[1:]...))

Unlike strings, rune slices are not immutable, so you can replace the first rune with ToUpper, which will take care of non-ASCII and/or multi-byte code points that do have upper cases (e.g. Russian) and leave alone those that don't (e.g. Asian scripts)

NOTE: there is a difference between UPPER case and TITLE case, which is simply explained here. In short, digraph characters like DŽ will have different title case (Dž, only first grapheme capitalized) and upper cases (DŽ, both graphemes capitalized). If you actually need titlecase, use unicode.ToTitle.

NOTE 2: converting to/from string to []rune involves copying, because you get a mutable slice from an immutable string. Do profile your application if you expect to use it in performance-sensitive code.

Playground: https://go.dev/play/p/HpCBM7cRflZ

<hr>

If you have a sizeable input string where a full rune slice conversion becomes too expensive, you can work around this using a capped strings.SplitN on some separator, essentially to extract the first word of the text and use only that in the conversion:

sep := &quot; &quot;
ss := strings.SplitN(s, sep, 2)

r := []rune(ss[0])
r[0] = unicode.ToUpper(r[0])

s = string(r) + sep + ss[1])

Benchmarking with a ~30K input string shows a significant difference:

go test -v -bench=. -benchmem
goos: darwin
goarch: arm64
pkg: example.com
BenchmarkRuneConv-10    	    6376	    183691 ns/op	  258049 B/op	       3 allocs/op
BenchmarkSplitN-10      	 1709989	       706.1 ns/op	    4152 B/op	       3 allocs/op
PASS
ok  	example.com	3.477s

答案2

得分: 0

实现所需结果的最简单方法是使用strings.ToUpper()函数。参考

    var input string = "the biggest ocean is the Pacific ocean"
	res := strings.ToUpper(input[:1]) + input[1:]

	fmt.Println(res)

或者你可以在goplayground上尝试。

英文:

The simplest way to achieve the desired result is to use strings.ToUpper() function. Refer

    var input string = &quot;the biggest ocean is the Pacific ocean&quot;
	res := strings.ToUpper(input[:1]) + input[1:]

	fmt.Println(res)

OR

You can try it on goplayground

答案3

得分: -1

获取第一个符文,将该符文转为标题大小写,并重新组装字符串:

句子 := "the biggest ocean is the Pacific ocean"
r, i := utf8.DecodeRuneInString(句子)
句子 = string(unicode.ToTitle(r)) + 句子[i:]
fmt.Println(句子)

英文:

Get the first rune, title case that rune and reassemble the string:

sentence := &quot;the biggest ocean is the Pacific ocean&quot;
r, i := utf8.DecodeRuneInString(sentence)
sentence = string(unicode.ToTitle(r)) + sentence[i:]
fmt.Println(sentence)

答案4

得分: -10

我为你有一个简单的解决方案。

这是我在Github上找到的一个项目的分支。

https://github.com/CleanMachine1/capitalise

要使用它,只需在终端中运行以下命令:

go mod init MODULENAME
go get github.com/cleanmachine1/capitalise

然后在你的代码中可以这样使用:


package main

import ("github.com/cleanmachine1/capitalise")

func main(){
 sentence = capitalise.First(sentence)
}
英文:

I have simple solution for you.

Its a fork I have of someones project on Github

https://github.com/CleanMachine1/capitalise

To use it just run in a terminal:

go mod init MODULENAME
go get github.com/cleanmachine1/capitalise

then in your code you can use


package main

import (&quot;github.com/cleanmachine1/capitalise&quot;)

func main(){
 sentence = capitalise.First(sentence)
}

huangapple
  • 本文由 发表于 2021年12月3日 05:01:36
  • 转载请务必保留本文链接:https://go.coder-hub.com/70206380.html
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