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  <div class="section" id="dynamic-url-dispatch">
<h1>Dynamic URL Dispatch<a class="headerlink" href="#dynamic-url-dispatch" title="Permalink to this headline">¶</a></h1>
<p>In the <a class="reference internal" href="static-dispatch.html"><em>previous example</em></a> we covered how to
statically configure Twisted Web to serve different content at different
URLs. The goal of this example is to show you how to do this dynamically
instead. Reading the previous installment if you haven&#8217;t already is suggested in
order to get an overview of how URLs are treated when using Twisted Web&#8217;s <a class="api reference external" href="https://twistedmatrix.com/documents/16.0.0/api/twisted.web.resource.html">resource</a> APIs.</p>
<p><a class="api reference external" href="https://twistedmatrix.com/documents/16.0.0/api/twisted.web.server.Site.html">Site</a> (the object which
associates a listening server port with the HTTP implementation), <a class="api reference external" href="https://twistedmatrix.com/documents/16.0.0/api/twisted.web.resource.Resource.html">Resource</a> (a convenient base class
to use when defining custom pages), and <a class="api reference external" href="https://twistedmatrix.com/documents/16.0.0/api/twisted.internet.reactor.html">reactor</a> (the object which implements the Twisted
main loop) return once again:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">twisted.web.server</span> <span class="kn">import</span> <span class="n">Site</span>
<span class="kn">from</span> <span class="nn">twisted.web.resource</span> <span class="kn">import</span> <span class="n">Resource</span>
<span class="kn">from</span> <span class="nn">twisted.internet</span> <span class="kn">import</span> <span class="n">reactor</span>
</pre></div>
</div>
<p>With that out of the way, here&#8217;s the interesting part of this
example. We&#8217;re going to define a resource which renders a whole-year
calendar. The year it will render the calendar for will be the year in
the request URL. So, for example, <code class="docutils literal"><span class="pre">/2009</span></code> will render a
calendar for 2009. First, here&#8217;s a resource that renders a calendar
for the year passed to its initializer:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">calendar</span> <span class="kn">import</span> <span class="n">calendar</span>

<span class="k">class</span> <span class="nc">YearPage</span><span class="p">(</span><span class="n">Resource</span><span class="p">):</span>
    <span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">year</span><span class="p">):</span>
        <span class="n">Resource</span><span class="o">.</span><span class="n">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">)</span>
        <span class="bp">self</span><span class="o">.</span><span class="n">year</span> <span class="o">=</span> <span class="n">year</span>

    <span class="k">def</span> <span class="nf">render_GET</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">request</span><span class="p">):</span>
        <span class="k">return</span> <span class="s">&quot;&lt;html&gt;&lt;body&gt;&lt;pre&gt;</span><span class="si">%s</span><span class="s">&lt;/pre&gt;&lt;/body&gt;&lt;/html&gt;&quot;</span> <span class="o">%</span> <span class="p">(</span><span class="n">calendar</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">year</span><span class="p">),)</span>
</pre></div>
</div>
<p>Pretty simple - not all that different from the first dynamic resource
demonstrated in <a class="reference internal" href="dynamic-content.html"><em>Generating a Page Dynamically</em></a> . Now here&#8217;s the resource that handles URLs with a year in them
by creating a suitable instance of this <code class="docutils literal"><span class="pre">YearPage</span></code> class:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="k">class</span> <span class="nc">Calendar</span><span class="p">(</span><span class="n">Resource</span><span class="p">):</span>
  <span class="k">def</span> <span class="nf">getChild</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">name</span><span class="p">,</span> <span class="n">request</span><span class="p">):</span>
      <span class="k">return</span> <span class="n">YearPage</span><span class="p">(</span><span class="nb">int</span><span class="p">(</span><span class="n">name</span><span class="p">))</span>
</pre></div>
</div>
<p>By implementing <a class="api reference external" href="https://twistedmatrix.com/documents/16.0.0/api/twisted.web.resource.Resource.getChild.html">getChild</a> here, we&#8217;ve just defined
how Twisted Web should find children of <code class="docutils literal"><span class="pre">Calendar</span></code> instances when
it&#8217;s resolving an URL into a resource. This implementation defines all integers
as the children of <code class="docutils literal"><span class="pre">Calendar</span></code> (and punts on error handling, more on
that later).</p>
<p>All that&#8217;s left is to create a <code class="docutils literal"><span class="pre">Site</span></code> using this resource as its
root and then start the reactor:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">root</span> <span class="o">=</span> <span class="n">Calendar</span><span class="p">()</span>
<span class="n">factory</span> <span class="o">=</span> <span class="n">Site</span><span class="p">(</span><span class="n">root</span><span class="p">)</span>
<span class="n">reactor</span><span class="o">.</span><span class="n">listenTCP</span><span class="p">(</span><span class="mi">8880</span><span class="p">,</span> <span class="n">factory</span><span class="p">)</span>
<span class="n">reactor</span><span class="o">.</span><span class="n">run</span><span class="p">()</span>
</pre></div>
</div>
<p>And that&#8217;s all. Any resource-based dynamic URL handling is going to look
basically like <code class="docutils literal"><span class="pre">Calendar.getChild</span></code> . Here&#8217;s the full example code:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">twisted.web.server</span> <span class="kn">import</span> <span class="n">Site</span>
<span class="kn">from</span> <span class="nn">twisted.web.resource</span> <span class="kn">import</span> <span class="n">Resource</span>
<span class="kn">from</span> <span class="nn">twisted.internet</span> <span class="kn">import</span> <span class="n">reactor</span>

<span class="kn">from</span> <span class="nn">calendar</span> <span class="kn">import</span> <span class="n">calendar</span>

<span class="k">class</span> <span class="nc">YearPage</span><span class="p">(</span><span class="n">Resource</span><span class="p">):</span>
    <span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">year</span><span class="p">):</span>
        <span class="n">Resource</span><span class="o">.</span><span class="n">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">)</span>
        <span class="bp">self</span><span class="o">.</span><span class="n">year</span> <span class="o">=</span> <span class="n">year</span>

    <span class="k">def</span> <span class="nf">render_GET</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">request</span><span class="p">):</span>
        <span class="k">return</span> <span class="s">&quot;&lt;html&gt;&lt;body&gt;&lt;pre&gt;</span><span class="si">%s</span><span class="s">&lt;/pre&gt;&lt;/body&gt;&lt;/html&gt;&quot;</span> <span class="o">%</span> <span class="p">(</span><span class="n">calendar</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">year</span><span class="p">),)</span>

<span class="k">class</span> <span class="nc">Calendar</span><span class="p">(</span><span class="n">Resource</span><span class="p">):</span>
  <span class="k">def</span> <span class="nf">getChild</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">name</span><span class="p">,</span> <span class="n">request</span><span class="p">):</span>
      <span class="k">return</span> <span class="n">YearPage</span><span class="p">(</span><span class="nb">int</span><span class="p">(</span><span class="n">name</span><span class="p">))</span>

<span class="n">root</span> <span class="o">=</span> <span class="n">Calendar</span><span class="p">()</span>
<span class="n">factory</span> <span class="o">=</span> <span class="n">Site</span><span class="p">(</span><span class="n">root</span><span class="p">)</span>
<span class="n">reactor</span><span class="o">.</span><span class="n">listenTCP</span><span class="p">(</span><span class="mi">8880</span><span class="p">,</span> <span class="n">factory</span><span class="p">)</span>
<span class="n">reactor</span><span class="o">.</span><span class="n">run</span><span class="p">()</span>
</pre></div>
</div>
</div>


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python-twisted-web 16.0.0-1 / usr / share / doc / python-twisted-web / howto / web-in-60 / dynamic-dispatch.html
