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number-parsing
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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Go by Example: Number Parsing</title>
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</head>
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<div class="example" id="number-parsing">
<h2><a href="./">Go by Example</a>: Number Parsing</h2>
<table>
<tr>
<td class="docs">
<p>Parsing numbers from strings is a basic but common task
in many programs; here’s how to do it in Go.</p>
</td>
<td class="code empty leading">
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<a href="https://go.dev/play/p/ZAMEid6Fpmu"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
<pre class="chroma"><code><span class="line"><span class="cl"><span class="kn">package</span> <span class="nx">main</span></span></span></code></pre>
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<tr>
<td class="docs">
<p>The built-in package <code>strconv</code> provides the number
parsing.</p>
</td>
<td class="code leading">
<pre class="chroma"><code><span class="line"><span class="cl"><span class="kn">import</span> <span class="p">(</span>
</span></span><span class="line"><span class="cl"> <span class="s">"fmt"</span>
</span></span><span class="line"><span class="cl"> <span class="s">"strconv"</span>
</span></span><span class="line"><span class="cl"><span class="p">)</span></span></span></code></pre>
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<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"><code><span class="line"><span class="cl"><span class="kd">func</span> <span class="nf">main</span><span class="p">()</span> <span class="p">{</span></span></span></code></pre>
</td>
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<tr>
<td class="docs">
<p>With <code>ParseFloat</code>, this <code>64</code> tells how many bits of
precision to parse.</p>
</td>
<td class="code leading">
<pre class="chroma"><code><span class="line"><span class="cl"> <span class="nx">f</span><span class="p">,</span> <span class="nx">_</span> <span class="o">:=</span> <span class="nx">strconv</span><span class="p">.</span><span class="nf">ParseFloat</span><span class="p">(</span><span class="s">"1.234"</span><span class="p">,</span> <span class="mi">64</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"> <span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">f</span><span class="p">)</span></span></span></code></pre>
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<td class="docs">
<p>For <code>ParseInt</code>, the <code>0</code> means infer the base from
the string. <code>64</code> requires that the result fit in 64
bits.</p>
</td>
<td class="code leading">
<pre class="chroma"><code><span class="line"><span class="cl"> <span class="nx">i</span><span class="p">,</span> <span class="nx">_</span> <span class="o">:=</span> <span class="nx">strconv</span><span class="p">.</span><span class="nf">ParseInt</span><span class="p">(</span><span class="s">"123"</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="mi">64</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"> <span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">i</span><span class="p">)</span></span></span></code></pre>
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<td class="docs">
<p><code>ParseInt</code> will recognize hex-formatted numbers.</p>
</td>
<td class="code leading">
<pre class="chroma"><code><span class="line"><span class="cl"> <span class="nx">d</span><span class="p">,</span> <span class="nx">_</span> <span class="o">:=</span> <span class="nx">strconv</span><span class="p">.</span><span class="nf">ParseInt</span><span class="p">(</span><span class="s">"0x1c8"</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="mi">64</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"> <span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">d</span><span class="p">)</span></span></span></code></pre>
</td>
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<tr>
<td class="docs">
<p>A <code>ParseUint</code> is also available.</p>
</td>
<td class="code leading">
<pre class="chroma"><code><span class="line"><span class="cl"> <span class="nx">u</span><span class="p">,</span> <span class="nx">_</span> <span class="o">:=</span> <span class="nx">strconv</span><span class="p">.</span><span class="nf">ParseUint</span><span class="p">(</span><span class="s">"789"</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="mi">64</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"> <span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">u</span><span class="p">)</span></span></span></code></pre>
</td>
</tr>
<tr>
<td class="docs">
<p><code>Atoi</code> is a convenience function for basic base-10
<code>int</code> parsing.</p>
</td>
<td class="code leading">
<pre class="chroma"><code><span class="line"><span class="cl"> <span class="nx">k</span><span class="p">,</span> <span class="nx">_</span> <span class="o">:=</span> <span class="nx">strconv</span><span class="p">.</span><span class="nf">Atoi</span><span class="p">(</span><span class="s">"135"</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"> <span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">k</span><span class="p">)</span></span></span></code></pre>
</td>
</tr>
<tr>
<td class="docs">
<p>Parse functions return an error on bad input.</p>
</td>
<td class="code">
<pre class="chroma"><code><span class="line"><span class="cl"> <span class="nx">_</span><span class="p">,</span> <span class="nx">e</span> <span class="o">:=</span> <span class="nx">strconv</span><span class="p">.</span><span class="nf">Atoi</span><span class="p">(</span><span class="s">"wat"</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"> <span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">e</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"><span class="p">}</span></span></span></code></pre>
</td>
</tr>
</table>
<table>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"><code><span class="line"><span class="cl"><span class="gp">$</span> go run number-parsing.go
</span></span><span class="line"><span class="cl"><span class="go">1.234
</span></span></span><span class="line"><span class="cl"><span class="go">123
</span></span></span><span class="line"><span class="cl"><span class="go">456
</span></span></span><span class="line"><span class="cl"><span class="go">789
</span></span></span><span class="line"><span class="cl"><span class="go">135
</span></span></span><span class="line"><span class="cl"><span class="go">strconv.ParseInt: parsing "wat": invalid syntax</span></span></span></code></pre>
</td>
</tr>
<tr>
<td class="docs">
<p>Next we’ll look at another common parsing task: URLs.</p>
</td>
<td class="code empty">
</td>
</tr>
</table>
<p class="next">
Next example: <a href="url-parsing">URL Parsing</a>.
</p>
<p class="footer">
by <a href="https://markmcgranaghan.com">Mark McGranaghan</a> and <a href="https://eli.thegreenplace.net">Eli Bendersky</a> | <a href="https://github.com/mmcgrana/gobyexample">source</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a>
</p>
</div>
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