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<!-- WARNING: THIS FILE WAS AUTOGENERATED! DO NOT EDIT! -->
<p>The majority of the time the default <a href="../explains/explaining_xt_components.html">ft components</a> are all you need (for example <code>Div</code>, <code>P</code>, <code>H1</code>, etc.).</p>
<div class="callout callout-style-default callout-tip callout-titled">
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Pre-requisite Knowledge
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<p>If you don’t know what an ft component is, you should read <a href="../explains/explaining_xt_components.html">the explaining ft components explainer first</a>.</p>
</div>
</div>
<p>However, there are many situations where you need a custom ft component that creates a unique HTML tag (for example <code>&lt;zero-md&gt;&lt;/zero-md&gt;</code>). There are many options in FastHTML to do this, and this section will walk through them. Generally you want to use the highest level option that fits your needs.</p>
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Real-world example
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<p><a href="https://isaac-flath.github.io/website/posts/boots/FasthtmlTutorial.html">This external tutorial</a> walks through a practical situation where you may want to create a custom HTML tag using a custom ft component. Seeing a real-world example is a good way to understand why the contents of this guide is useful.</p>
</div>
</div>
<section id="notstr" class="level2">
<h2 class="anchored" data-anchor-id="notstr">NotStr</h2>
<p>The first way is to use the <code>NotStr</code> class to use an HTML tag as a string. It works as a one-off but quickly becomes harder to work with as complexity grows. However we can see that you can genenrate the same xml using <code>NotStr</code> as the out-of-the-box components.</p>
<div id="cell-5" class="cell">
<div class="sourceCode cell-code" id="cb1"><pre class="sourceCode python code-with-copy"><code class="sourceCode python"><span id="cb1-1"><a href="#cb1-1" aria-hidden="true" tabindex="-1"></a><span class="im">from</span> fasthtml.common <span class="im">import</span> NotStr,Div, to_xml</span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
</div>
<div id="cell-6" class="cell">
<div class="sourceCode cell-code" id="cb2"><pre class="sourceCode python code-with-copy"><code class="sourceCode python"><span id="cb2-1"><a href="#cb2-1" aria-hidden="true" tabindex="-1"></a>div_NotStr <span class="op">=</span> NotStr(<span class="st">'&lt;div&gt;&lt;/div&gt;'</span>) </span>
<span id="cb2-2"><a href="#cb2-2" aria-hidden="true" tabindex="-1"></a><span class="bu">print</span>(div_NotStr)</span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
<div class="cell-output cell-output-stdout">
<pre><code>&lt;div&gt;&lt;/div&gt;</code></pre>
</div>
</div>
</section>
<section id="automatic-creation" class="level2">
<h2 class="anchored" data-anchor-id="automatic-creation">Automatic Creation</h2>
<p>The next (and better) approach is to let FastHTML generate the component function for you. As you can see in our <code>assert</code> this creates a function that creates the HTML just as we wanted. This works even though there is not a <code>Some_never_before_used_tag</code> function in the <code>fasthtml.components</code> source code (you can verify this yourself by looking at the source code).</p>
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<p>Typically these tags are needed because a CSS or Javascript library created a new XML tag that isn’t default HTML. For example the <code>zero-md</code> javascript library looks for a <code>&lt;zero-md&gt;&lt;/zero-md&gt;</code> tag to know what to run its javascript code on. Most CSS libraries work by creating styling based on the <code>class</code> attribute, but they can also apply styling to an arbitrary HTML tag that they made up.</p>
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<div id="cell-8" class="cell">
<div class="sourceCode cell-code" id="cb4"><pre class="sourceCode python code-with-copy"><code class="sourceCode python"><span id="cb4-1"><a href="#cb4-1" aria-hidden="true" tabindex="-1"></a><span class="im">from</span> fasthtml.components <span class="im">import</span> Some_never_before_used_tag</span>
<span id="cb4-2"><a href="#cb4-2" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb4-3"><a href="#cb4-3" aria-hidden="true" tabindex="-1"></a>Some_never_before_used_tag()</span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
<div class="cell-output cell-output-display cell-output-markdown">
<div class="sourceCode" id="cb5"><pre class="sourceCode html code-with-copy"><code class="sourceCode html"><span id="cb5-1"><a href="#cb5-1" aria-hidden="true" tabindex="-1"></a><span class="dt">&lt;</span><span class="kw">some-never-before-used-tag</span><span class="dt">&gt;&lt;/</span><span class="kw">some-never-before-used-tag</span><span class="dt">&gt;</span></span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
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</div>
</section>
<section id="manual-creation" class="level2">
<h2 class="anchored" data-anchor-id="manual-creation">Manual Creation</h2>
<p>The automatic creation isn’t magic. It’s just calling a python function <a href="https://www.fastht.ml/docs/api/components.html#__getattr__"><code>__getattr__</code></a> and you can call it yourself to get the same result.</p>
<div id="cell-11" class="cell">
<div class="sourceCode cell-code" id="cb6"><pre class="sourceCode python code-with-copy"><code class="sourceCode python"><span id="cb6-1"><a href="#cb6-1" aria-hidden="true" tabindex="-1"></a><span class="im">import</span> fasthtml</span>
<span id="cb6-2"><a href="#cb6-2" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb6-3"><a href="#cb6-3" aria-hidden="true" tabindex="-1"></a>auto_called <span class="op">=</span> fasthtml.components.Some_never_before_used_tag()</span>
<span id="cb6-4"><a href="#cb6-4" aria-hidden="true" tabindex="-1"></a>manual_called <span class="op">=</span> fasthtml.components.<span class="fu">__getattr__</span>(<span class="st">'Some_never_before_used_tag'</span>)()</span>
<span id="cb6-5"><a href="#cb6-5" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb6-6"><a href="#cb6-6" aria-hidden="true" tabindex="-1"></a><span class="co"># Proving they generate the same xml</span></span>
<span id="cb6-7"><a href="#cb6-7" aria-hidden="true" tabindex="-1"></a><span class="cf">assert</span> to_xml(auto_called) <span class="op">==</span> to_xml(manual_called)</span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
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<p>Knowing that, we know that it’s possible to create a different function that has different behavior than FastHTMLs default behavior by modifying how the <code>___getattr__</code> function creates the components! It’s only a few lines of code and reading that what it does is a great way to understand components more deeply.</p>
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<p>Dunder methods and functions are special functions that have double underscores at the beginning and end of their name. They are called at specific times in python so you can use them to cause customized behavior that makes sense for your specific use case. They can appear magical if you don’t know how python works, but they are extremely commonly used to modify python’s default behavior (<code>__init__</code> is probably the most common one).</p>
<p>In a module <a href="https://www.fastht.ml/docs/api/components.html#__getattr__"><code>__getattr__</code></a> is&nbsp;called to get an attribute. In <code>fasthtml.components</code>, this is defined to create components automatically for you.</p>
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<p>For example if you want a component that creates <code>&lt;path&gt;&lt;/path&gt;</code> that doesn’t conflict names with <a href="https://docs.python.org/3/library/pathlib.html#pathlib.Path"><code>pathlib.Path</code></a> you can do that. FastHTML automatically creates new components with a 1:1 mapping and a consistent name, which is almost always what you want. But in some cases you may want to customize that and you can use the <a href="https://www.fastht.ml/docs/api/components.html#ft_hx"><code>ft_hx</code></a> function to do that differently than the default.</p>
<div id="cell-14" class="cell">
<div class="sourceCode cell-code" id="cb7"><pre class="sourceCode python code-with-copy"><code class="sourceCode python"><span id="cb7-1"><a href="#cb7-1" aria-hidden="true" tabindex="-1"></a><span class="im">from</span> fasthtml.common <span class="im">import</span> ft_hx</span>
<span id="cb7-2"><a href="#cb7-2" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb7-3"><a href="#cb7-3" aria-hidden="true" tabindex="-1"></a><span class="kw">def</span> ft_path(<span class="op">*</span>c, target_id<span class="op">=</span><span class="va">None</span>, <span class="op">**</span>kwargs): </span>
<span id="cb7-4"><a href="#cb7-4" aria-hidden="true" tabindex="-1"></a>    <span class="cf">return</span> ft_hx(<span class="st">'path'</span>, <span class="op">*</span>c, target_id<span class="op">=</span>target_id, <span class="op">**</span>kwargs)</span>
<span id="cb7-5"><a href="#cb7-5" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb7-6"><a href="#cb7-6" aria-hidden="true" tabindex="-1"></a>ft_path()</span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
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<div class="sourceCode" id="cb8"><pre class="sourceCode html code-with-copy"><code class="sourceCode html"><span id="cb8-1"><a href="#cb8-1" aria-hidden="true" tabindex="-1"></a><span class="dt">&lt;</span><span class="kw">path</span><span class="dt">&gt;&lt;/</span><span class="kw">path</span><span class="dt">&gt;</span></span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
</div>
</div>
<p>We can add any behavior in that function that we need to, so let’s go through some progressively complex examples that you may need in some of your projects.</p>
<section id="underscores-in-tags" class="level3">
<h3 class="anchored" data-anchor-id="underscores-in-tags">Underscores in tags</h3>
<p>Now that we understand how FastHTML generates components, we can create our own in all kinds of ways. For example, maybe we need a weird HTML tag that uses underscores. FastHTML replaces <code>_</code> with <code>-</code> in tags because underscores in tags are highly unusual and rarely what you want, though it does come up rarely.</p>
<div id="cell-18" class="cell">
<div class="sourceCode cell-code" id="cb9"><pre class="sourceCode python code-with-copy"><code class="sourceCode python"><span id="cb9-1"><a href="#cb9-1" aria-hidden="true" tabindex="-1"></a><span class="kw">def</span> tag_with_underscores(<span class="op">*</span>c, target_id<span class="op">=</span><span class="va">None</span>, <span class="op">**</span>kwargs): </span>
<span id="cb9-2"><a href="#cb9-2" aria-hidden="true" tabindex="-1"></a>    <span class="cf">return</span> ft_hx(<span class="st">'tag_with_underscores'</span>, <span class="op">*</span>c, target_id<span class="op">=</span>target_id, <span class="op">**</span>kwargs)</span>
<span id="cb9-3"><a href="#cb9-3" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb9-4"><a href="#cb9-4" aria-hidden="true" tabindex="-1"></a>tag_with_underscores()</span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
<div class="cell-output cell-output-display cell-output-markdown">
<div class="sourceCode" id="cb10"><pre class="sourceCode html code-with-copy"><code class="sourceCode html"><span id="cb10-1"><a href="#cb10-1" aria-hidden="true" tabindex="-1"></a><span class="dt">&lt;</span><span class="kw">tag_with_underscores</span><span class="dt">&gt;&lt;/</span><span class="kw">tag_with_underscores</span><span class="dt">&gt;</span></span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
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</div>
</section>
<section id="symbols-ie-in-tags" class="level3">
<h3 class="anchored" data-anchor-id="symbols-ie-in-tags">Symbols (ie @) in tags</h3>
<p>Sometimes you may need to use a tag that uses characters that are not allowed in function names in python (again, very unusual).</p>
<div id="cell-21" class="cell">
<div class="sourceCode cell-code" id="cb11"><pre class="sourceCode python code-with-copy"><code class="sourceCode python"><span id="cb11-1"><a href="#cb11-1" aria-hidden="true" tabindex="-1"></a><span class="kw">def</span> tag_with_AtSymbol(<span class="op">*</span>c, target_id<span class="op">=</span><span class="va">None</span>, <span class="op">**</span>kwargs): </span>
<span id="cb11-2"><a href="#cb11-2" aria-hidden="true" tabindex="-1"></a>    <span class="cf">return</span> ft_hx(<span class="st">'tag-with-@symbol'</span>, <span class="op">*</span>c, target_id<span class="op">=</span>target_id, <span class="op">**</span>kwargs)</span>
<span id="cb11-3"><a href="#cb11-3" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb11-4"><a href="#cb11-4" aria-hidden="true" tabindex="-1"></a>tag_with_AtSymbol()</span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
<div class="cell-output cell-output-display cell-output-markdown">
<div class="sourceCode" id="cb12"><pre class="sourceCode html code-with-copy"><code class="sourceCode html"><span id="cb12-1"><a href="#cb12-1" aria-hidden="true" tabindex="-1"></a><span class="dt">&lt;</span><span class="kw">tag-with-</span><span class="er">@</span><span class="ot">symbol</span><span class="dt">&gt;&lt;/</span><span class="kw">tag-with-</span><span class="er">@symbol</span><span class="dt">&gt;</span></span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
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</div>
</section>
<section id="symbols-ie-in-tag-attributes" class="level3">
<h3 class="anchored" data-anchor-id="symbols-ie-in-tag-attributes">Symbols (ie @) in tag attributes</h3>
<p>It also may be that an argument in an HTML tag uses characters that can’t be used in python arguments. To handle these you can define those args using a dictionary.</p>
<div id="cell-24" class="cell">
<div class="sourceCode cell-code" id="cb13"><pre class="sourceCode python code-with-copy"><code class="sourceCode python"><span id="cb13-1"><a href="#cb13-1" aria-hidden="true" tabindex="-1"></a>Div(normal_arg<span class="op">=</span><span class="st">'normal stuff'</span>,<span class="op">**</span>{<span class="st">'notNormal:arg:with_varing@symbols!'</span>:<span class="st">'123'</span>})</span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
<div class="cell-output cell-output-display cell-output-markdown">
<div class="sourceCode" id="cb14"><pre class="sourceCode html code-with-copy"><code class="sourceCode html"><span id="cb14-1"><a href="#cb14-1" aria-hidden="true" tabindex="-1"></a><span class="dt">&lt;</span><span class="kw">div</span><span class="ot"> normal-arg</span><span class="op">=</span><span class="st">"normal stuff"</span><span class="ot"> notnormal:arg:with_varing</span><span class="er">@</span><span class="ot">symbols</span><span class="er">!</span><span class="op">=</span><span class="st">"123"</span><span class="dt">&gt;&lt;/</span><span class="kw">div</span><span class="dt">&gt;</span></span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
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              fn.apply(this, args);
              timer = throttle = false;
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});
</script>
</div> <!-- /content -->




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