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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Go by Example 中文版: 字符串格式化</title>
<link rel=stylesheet href="site.css">
</head>
<script>
onkeydown = (e) => {
if (e.key == "ArrowLeft") {
window.location.href = 'string-functions';
}
if (e.key == "ArrowRight") {
window.location.href = 'text-templates';
}
}
</script>
<body>
<div class="example" id="string-formatting">
<h2><a href="./">Go by Example 中文版</a>: 字符串格式化</h2>
<table>
<tr>
<td class="docs">
<p>Go 在传统的 <code>printf</code> 中对字符串格式化提供了优异的支持。
这儿有一些基本的字符串格式化的任务的例子。</p>
</td>
<td class="code empty leading">
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<a href="https://play.studygolang.com/p/XY3ad4TXm3J"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
<pre class="chroma"><span class="kn">package</span> <span class="nx">main</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"><span class="kn">import</span> <span class="p">(</span>
<span class="s">"fmt"</span>
<span class="s">"os"</span>
<span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"><span class="kd">type</span> <span class="nx">point</span> <span class="kd">struct</span> <span class="p">{</span>
<span class="nx">x</span><span class="p">,</span> <span class="nx">y</span> <span class="kt">int</span>
<span class="p">}</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"><span class="kd">func</span> <span class="nf">main</span><span class="p">()</span> <span class="p">{</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>Go 提供了一些用于格式化常规值的打印“动词”。
例如，这样打印 <code>point</code> 结构体的实例。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">p</span> <span class="o">:=</span> <span class="nx">point</span><span class="p">{</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">}</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Printf</span><span class="p">(</span><span class="s">"struct1: %v\n"</span><span class="p">,</span> <span class="nx">p</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>如果值是一个结构体，<code>%+v</code> 的格式化输出内容将包括结构体的字段名。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Printf</span><span class="p">(</span><span class="s">"struct2: %+v\n"</span><span class="p">,</span> <span class="nx">p</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p><code>%#v</code> 根据 Go 语法输出值，即会产生该值的源码片段。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Printf</span><span class="p">(</span><span class="s">"struct3: %#v\n"</span><span class="p">,</span> <span class="nx">p</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>需要打印值的类型，使用 <code>%T</code>。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Printf</span><span class="p">(</span><span class="s">"type: %T\n"</span><span class="p">,</span> <span class="nx">p</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>格式化布尔值很简单。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Printf</span><span class="p">(</span><span class="s">"bool: %t\n"</span><span class="p">,</span> <span class="kc">true</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>格式化整型数有多种方式，使用 <code>%d</code> 进行标准的十进制格式化。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Printf</span><span class="p">(</span><span class="s">"int: %d\n"</span><span class="p">,</span> <span class="mi">123</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>这个输出二进制表示形式。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Printf</span><span class="p">(</span><span class="s">"bin: %b\n"</span><span class="p">,</span> <span class="mi">14</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>输出给定整数的对应字符。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Printf</span><span class="p">(</span><span class="s">"char: %c\n"</span><span class="p">,</span> <span class="mi">33</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p><code>%x</code> 提供了十六进制编码。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Printf</span><span class="p">(</span><span class="s">"hex: %x\n"</span><span class="p">,</span> <span class="mi">456</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>同样的，也为浮点型提供了多种格式化选项。
使用 <code>%f</code> 进行最基本的十进制格式化。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Printf</span><span class="p">(</span><span class="s">"float1: %f\n"</span><span class="p">,</span> <span class="mf">78.9</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p><code>%e</code> 和 <code>%E</code> 将浮点型格式化为（稍微有一点不同的）科学记数法表示形式。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Printf</span><span class="p">(</span><span class="s">"float2: %e\n"</span><span class="p">,</span> <span class="mf">123400000.0</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Printf</span><span class="p">(</span><span class="s">"float3: %E\n"</span><span class="p">,</span> <span class="mf">123400000.0</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>使用 <code>%s</code> 进行基本的字符串输出。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Printf</span><span class="p">(</span><span class="s">"str1: %s\n"</span><span class="p">,</span> <span class="s">"\"string\""</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>像 Go 源代码中那样带有双引号的输出，使用 <code>%q</code>。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Printf</span><span class="p">(</span><span class="s">"str2: %q\n"</span><span class="p">,</span> <span class="s">"\"string\""</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>和上面的整型数一样，<code>%x</code> 输出使用 base-16 编码的字符串，
每个字节使用 2 个字符表示。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Printf</span><span class="p">(</span><span class="s">"str3: %x\n"</span><span class="p">,</span> <span class="s">"hex this"</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>要输出一个指针的值，使用 <code>%p</code>。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Printf</span><span class="p">(</span><span class="s">"pointer: %p\n"</span><span class="p">,</span> <span class="o">&</span><span class="nx">p</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>格式化数字时，您经常会希望控制输出结果的宽度和精度。
要指定整数的宽度，请在动词 “%” 之后使用数字。
默认情况下，结果会右对齐并用空格填充。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Printf</span><span class="p">(</span><span class="s">"width1: |%6d|%6d|\n"</span><span class="p">,</span> <span class="mi">12</span><span class="p">,</span> <span class="mi">345</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>你也可以指定浮点型的输出宽度，同时也可以通过 <code>宽度.精度</code> 的语法来指定输出的精度。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Printf</span><span class="p">(</span><span class="s">"width2: |%6.2f|%6.2f|\n"</span><span class="p">,</span> <span class="mf">1.2</span><span class="p">,</span> <span class="mf">3.45</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>要左对齐，使用 <code>-</code> 标志。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Printf</span><span class="p">(</span><span class="s">"width3: |%-6.2f|%-6.2f|\n"</span><span class="p">,</span> <span class="mf">1.2</span><span class="p">,</span> <span class="mf">3.45</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>你也许也想控制字符串输出时的宽度，特别是要确保他们在类表格输出时的对齐。
这是基本的宽度右对齐方法。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Printf</span><span class="p">(</span><span class="s">"width4: |%6s|%6s|\n"</span><span class="p">,</span> <span class="s">"foo"</span><span class="p">,</span> <span class="s">"b"</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>要左对齐，和数字一样，使用 <code>-</code> 标志。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Printf</span><span class="p">(</span><span class="s">"width5: |%-6s|%-6s|\n"</span><span class="p">,</span> <span class="s">"foo"</span><span class="p">,</span> <span class="s">"b"</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>到目前为止，我们已经看过 <code>Printf</code> 了，
它通过 <code>os.Stdout</code> 输出格式化的字符串。
<code>Sprintf</code> 则格式化并返回一个字符串而没有任何输出。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">s</span> <span class="o">:=</span> <span class="nx">fmt</span><span class="p">.</span><span class="nf">Sprintf</span><span class="p">(</span><span class="s">"sprintf: a %s"</span><span class="p">,</span> <span class="s">"string"</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">s</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>你可以使用 <code>Fprintf</code> 来格式化并输出到 <code>io.Writers</code> 而不是 <code>os.Stdout</code>。</p>
</td>
<td class="code">
<pre class="chroma">
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Fprintf</span><span class="p">(</span><span class="nx">os</span><span class="p">.</span><span class="nx">Stderr</span><span class="p">,</span> <span class="s">"io: an %s\n"</span><span class="p">,</span> <span class="s">"error"</span><span class="p">)</span>
<span class="p">}</span>
</pre>
</td>
</tr>
</table>
<table>
<tr>
<td class="docs">
</td>
<td class="code">
<pre class="chroma"><span class="gp">$</span> go run string-formatting.go
<span class="go">struct1: {1 2}
</span><span class="go">struct2: {x:1 y:2}
</span><span class="go">struct3: main.point{x:1, y:2}
</span><span class="go">type: main.point
</span><span class="go">bool: true
</span><span class="go">int: 123
</span><span class="go">bin: 1110
</span><span class="go">char: !
</span><span class="go">hex: 1c8
</span><span class="go">float1: 78.900000
</span><span class="go">float2: 1.234000e+08
</span><span class="go">float3: 1.234000E+08
</span><span class="go">str1: "string"
</span><span class="go">str2: "\"string\""
</span><span class="go">str3: 6865782074686973
</span><span class="go">pointer: 0xc0000ba000
</span><span class="go">width1: | 12| 345|
</span><span class="go">width2: | 1.20| 3.45|
</span><span class="go">width3: |1.20 |3.45 |
</span><span class="go">width4: | foo| b|
</span><span class="go">width5: |foo |b |
</span><span class="go">sprintf: a string
</span><span class="go">io: an error</span></pre>
</td>
</tr>
</table>
<p class="next">
下一个例子: <a href="text-templates">文本模板</a>
</p>
<p class="footer">
<a href="https://twitter.com/mmcgrana">@mmcgrana</a> 和<a href="https://eli.thegreenplace.net">Eli Bendersky</a>编写 | <a href="https://github.com/gobyexample-cn">gobyexample-cn</a> 翻译 | <a href="https://github.com/gobyexample-cn/gobyexample/issues">反馈</a> | <a href="https://github.com/gobyexample-cn/gobyexample">源码</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a> </p>
</p>
</div>
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