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  <div class="section" id="custom-type-example">
<h1>Custom Type Example<a class="headerlink" href="#custom-type-example" title="Permalink to this headline"></a></h1>
<p>This is an example of using a custom type with PyMongo. The example
here is a bit contrived, but shows how to use a
<a class="reference internal" href="../api/pymongo/son_manipulator.html#pymongo.son_manipulator.SONManipulator" title="pymongo.son_manipulator.SONManipulator"><tt class="xref py py-class docutils literal"><span class="pre">SONManipulator</span></tt></a> to manipulate
documents as they are saved or retrieved from MongoDB. More
specifically, it shows a couple different mechanisms for working with
custom datatypes in PyMongo.</p>
<div class="section" id="setup">
<h2>Setup<a class="headerlink" href="#setup" title="Permalink to this headline"></a></h2>
<p>We&#8217;ll start by getting a clean database to use for the example:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="kn">from</span> <span class="nn">pymongo.mongo_client</span> <span class="kn">import</span> <span class="n">MongoClient</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">client</span> <span class="o">=</span> <span class="n">MongoClient</span><span class="p">()</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">client</span><span class="o">.</span><span class="n">drop_database</span><span class="p">(</span><span class="s">&quot;custom_type_example&quot;</span><span class="p">)</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">db</span> <span class="o">=</span> <span class="n">client</span><span class="o">.</span><span class="n">custom_type_example</span>
</pre></div>
</div>
<p>Since the purpose of the example is to demonstrate working with custom
types, we&#8217;ll need a custom datatype to use. Here we define the aptly
named <tt class="xref py py-class docutils literal"><span class="pre">Custom</span></tt> class, which has a single method, <tt class="xref py py-meth docutils literal"><span class="pre">x()</span></tt>:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="k">class</span> <span class="nc">Custom</span><span class="p">(</span><span class="nb">object</span><span class="p">):</span>
<span class="gp">... </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">x</span><span class="p">):</span>
<span class="gp">... </span>    <span class="bp">self</span><span class="o">.</span><span class="n">__x</span> <span class="o">=</span> <span class="n">x</span>
<span class="gp">...</span>
<span class="gp">... </span>  <span class="k">def</span> <span class="nf">x</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="gp">... </span>    <span class="k">return</span> <span class="bp">self</span><span class="o">.</span><span class="n">__x</span>
<span class="gp">...</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">foo</span> <span class="o">=</span> <span class="n">Custom</span><span class="p">(</span><span class="mi">10</span><span class="p">)</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">foo</span><span class="o">.</span><span class="n">x</span><span class="p">()</span>
<span class="go">10</span>
</pre></div>
</div>
<p>When we try to save an instance of <tt class="xref py py-class docutils literal"><span class="pre">Custom</span></tt> with PyMongo, we&#8217;ll
get an <a class="reference internal" href="../api/bson/errors.html#bson.errors.InvalidDocument" title="bson.errors.InvalidDocument"><tt class="xref py py-class docutils literal"><span class="pre">InvalidDocument</span></tt></a> exception:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">db</span><span class="o">.</span><span class="n">test</span><span class="o">.</span><span class="n">insert</span><span class="p">({</span><span class="s">&quot;custom&quot;</span><span class="p">:</span> <span class="n">Custom</span><span class="p">(</span><span class="mi">5</span><span class="p">)})</span>
<span class="gt">Traceback (most recent call last):</span>
<span class="gr">InvalidDocument</span>: <span class="n">cannot convert value of type &lt;class &#39;Custom&#39;&gt; to bson</span>
</pre></div>
</div>
</div>
<div class="section" id="manual-encoding">
<h2>Manual Encoding<a class="headerlink" href="#manual-encoding" title="Permalink to this headline"></a></h2>
<p>One way to work around this is to manipulate our data into something
we <em>can</em> save with PyMongo. To do so we define two methods,
<tt class="xref py py-meth docutils literal"><span class="pre">encode_custom()</span></tt> and <tt class="xref py py-meth docutils literal"><span class="pre">decode_custom()</span></tt>:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="k">def</span> <span class="nf">encode_custom</span><span class="p">(</span><span class="n">custom</span><span class="p">):</span>
<span class="gp">... </span>  <span class="k">return</span> <span class="p">{</span><span class="s">&quot;_type&quot;</span><span class="p">:</span> <span class="s">&quot;custom&quot;</span><span class="p">,</span> <span class="s">&quot;x&quot;</span><span class="p">:</span> <span class="n">custom</span><span class="o">.</span><span class="n">x</span><span class="p">()}</span>
<span class="gp">...</span>
<span class="gp">&gt;&gt;&gt; </span><span class="k">def</span> <span class="nf">decode_custom</span><span class="p">(</span><span class="n">document</span><span class="p">):</span>
<span class="gp">... </span>  <span class="k">assert</span> <span class="n">document</span><span class="p">[</span><span class="s">&quot;_type&quot;</span><span class="p">]</span> <span class="o">==</span> <span class="s">&quot;custom&quot;</span>
<span class="gp">... </span>  <span class="k">return</span> <span class="n">Custom</span><span class="p">(</span><span class="n">document</span><span class="p">[</span><span class="s">&quot;x&quot;</span><span class="p">])</span>
<span class="gp">...</span>
</pre></div>
</div>
<p>We can now manually encode and decode <tt class="xref py py-class docutils literal"><span class="pre">Custom</span></tt> instances and
use them with PyMongo:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">db</span><span class="o">.</span><span class="n">test</span><span class="o">.</span><span class="n">insert</span><span class="p">({</span><span class="s">&quot;custom&quot;</span><span class="p">:</span> <span class="n">encode_custom</span><span class="p">(</span><span class="n">Custom</span><span class="p">(</span><span class="mi">5</span><span class="p">))})</span>
<span class="go">ObjectId(&#39;...&#39;)</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">db</span><span class="o">.</span><span class="n">test</span><span class="o">.</span><span class="n">find_one</span><span class="p">()</span>
<span class="go">{u&#39;_id&#39;: ObjectId(&#39;...&#39;), u&#39;custom&#39;: {u&#39;x&#39;: 5, u&#39;_type&#39;: u&#39;custom&#39;}}</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">decode_custom</span><span class="p">(</span><span class="n">db</span><span class="o">.</span><span class="n">test</span><span class="o">.</span><span class="n">find_one</span><span class="p">()[</span><span class="s">&quot;custom&quot;</span><span class="p">])</span>
<span class="go">&lt;Custom object at ...&gt;</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">decode_custom</span><span class="p">(</span><span class="n">db</span><span class="o">.</span><span class="n">test</span><span class="o">.</span><span class="n">find_one</span><span class="p">()[</span><span class="s">&quot;custom&quot;</span><span class="p">])</span><span class="o">.</span><span class="n">x</span><span class="p">()</span>
<span class="go">5</span>
</pre></div>
</div>
</div>
<div class="section" id="automatic-encoding-and-decoding">
<h2>Automatic Encoding and Decoding<a class="headerlink" href="#automatic-encoding-and-decoding" title="Permalink to this headline"></a></h2>
<p>Needless to say, that was a little unwieldy. Let&#8217;s make this a bit
more seamless by creating a new
<a class="reference internal" href="../api/pymongo/son_manipulator.html#pymongo.son_manipulator.SONManipulator" title="pymongo.son_manipulator.SONManipulator"><tt class="xref py py-class docutils literal"><span class="pre">SONManipulator</span></tt></a>.
<a class="reference internal" href="../api/pymongo/son_manipulator.html#pymongo.son_manipulator.SONManipulator" title="pymongo.son_manipulator.SONManipulator"><tt class="xref py py-class docutils literal"><span class="pre">SONManipulator</span></tt></a> instances allow you
to specify transformations to be applied automatically by PyMongo:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="kn">from</span> <span class="nn">pymongo.son_manipulator</span> <span class="kn">import</span> <span class="n">SONManipulator</span>
<span class="gp">&gt;&gt;&gt; </span><span class="k">class</span> <span class="nc">Transform</span><span class="p">(</span><span class="n">SONManipulator</span><span class="p">):</span>
<span class="gp">... </span>  <span class="k">def</span> <span class="nf">transform_incoming</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">son</span><span class="p">,</span> <span class="n">collection</span><span class="p">):</span>
<span class="gp">... </span>    <span class="k">for</span> <span class="p">(</span><span class="n">key</span><span class="p">,</span> <span class="n">value</span><span class="p">)</span> <span class="ow">in</span> <span class="n">son</span><span class="o">.</span><span class="n">items</span><span class="p">():</span>
<span class="gp">... </span>      <span class="k">if</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">value</span><span class="p">,</span> <span class="n">Custom</span><span class="p">):</span>
<span class="gp">... </span>        <span class="n">son</span><span class="p">[</span><span class="n">key</span><span class="p">]</span> <span class="o">=</span> <span class="n">encode_custom</span><span class="p">(</span><span class="n">value</span><span class="p">)</span>
<span class="gp">... </span>      <span class="k">elif</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">value</span><span class="p">,</span> <span class="nb">dict</span><span class="p">):</span> <span class="c"># Make sure we recurse into sub-docs</span>
<span class="gp">... </span>        <span class="n">son</span><span class="p">[</span><span class="n">key</span><span class="p">]</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">transform_incoming</span><span class="p">(</span><span class="n">value</span><span class="p">,</span> <span class="n">collection</span><span class="p">)</span>
<span class="gp">... </span>    <span class="k">return</span> <span class="n">son</span>
<span class="gp">...</span>
<span class="gp">... </span>  <span class="k">def</span> <span class="nf">transform_outgoing</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">son</span><span class="p">,</span> <span class="n">collection</span><span class="p">):</span>
<span class="gp">... </span>    <span class="k">for</span> <span class="p">(</span><span class="n">key</span><span class="p">,</span> <span class="n">value</span><span class="p">)</span> <span class="ow">in</span> <span class="n">son</span><span class="o">.</span><span class="n">items</span><span class="p">():</span>
<span class="gp">... </span>      <span class="k">if</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">value</span><span class="p">,</span> <span class="nb">dict</span><span class="p">):</span>
<span class="gp">... </span>        <span class="k">if</span> <span class="s">&quot;_type&quot;</span> <span class="ow">in</span> <span class="n">value</span> <span class="ow">and</span> <span class="n">value</span><span class="p">[</span><span class="s">&quot;_type&quot;</span><span class="p">]</span> <span class="o">==</span> <span class="s">&quot;custom&quot;</span><span class="p">:</span>
<span class="gp">... </span>          <span class="n">son</span><span class="p">[</span><span class="n">key</span><span class="p">]</span> <span class="o">=</span> <span class="n">decode_custom</span><span class="p">(</span><span class="n">value</span><span class="p">)</span>
<span class="gp">... </span>        <span class="k">else</span><span class="p">:</span> <span class="c"># Again, make sure to recurse into sub-docs</span>
<span class="gp">... </span>          <span class="n">son</span><span class="p">[</span><span class="n">key</span><span class="p">]</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">transform_outgoing</span><span class="p">(</span><span class="n">value</span><span class="p">,</span> <span class="n">collection</span><span class="p">)</span>
<span class="gp">... </span>    <span class="k">return</span> <span class="n">son</span>
<span class="gp">...</span>
</pre></div>
</div>
<p>Now we add our manipulator to the <a class="reference internal" href="../api/pymongo/database.html#pymongo.database.Database" title="pymongo.database.Database"><tt class="xref py py-class docutils literal"><span class="pre">Database</span></tt></a>:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">db</span><span class="o">.</span><span class="n">add_son_manipulator</span><span class="p">(</span><span class="n">Transform</span><span class="p">())</span>
</pre></div>
</div>
<p>After doing so we can save and restore <tt class="xref py py-class docutils literal"><span class="pre">Custom</span></tt> instances seamlessly:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">db</span><span class="o">.</span><span class="n">test</span><span class="o">.</span><span class="n">remove</span><span class="p">()</span> <span class="c"># remove whatever has already been saved</span>
<span class="go">{...}</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">db</span><span class="o">.</span><span class="n">test</span><span class="o">.</span><span class="n">insert</span><span class="p">({</span><span class="s">&quot;custom&quot;</span><span class="p">:</span> <span class="n">Custom</span><span class="p">(</span><span class="mi">5</span><span class="p">)})</span>
<span class="go">ObjectId(&#39;...&#39;)</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">db</span><span class="o">.</span><span class="n">test</span><span class="o">.</span><span class="n">find_one</span><span class="p">()</span>
<span class="go">{u&#39;_id&#39;: ObjectId(&#39;...&#39;), u&#39;custom&#39;: &lt;Custom object at ...&gt;}</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">db</span><span class="o">.</span><span class="n">test</span><span class="o">.</span><span class="n">find_one</span><span class="p">()[</span><span class="s">&quot;custom&quot;</span><span class="p">]</span><span class="o">.</span><span class="n">x</span><span class="p">()</span>
<span class="go">5</span>
</pre></div>
</div>
<p>If we get a new <a class="reference internal" href="../api/pymongo/database.html#pymongo.database.Database" title="pymongo.database.Database"><tt class="xref py py-class docutils literal"><span class="pre">Database</span></tt></a> instance we&#8217;ll
clear out the <a class="reference internal" href="../api/pymongo/son_manipulator.html#pymongo.son_manipulator.SONManipulator" title="pymongo.son_manipulator.SONManipulator"><tt class="xref py py-class docutils literal"><span class="pre">SONManipulator</span></tt></a>
instance we added:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">db</span> <span class="o">=</span> <span class="n">client</span><span class="o">.</span><span class="n">custom_type_example</span>
</pre></div>
</div>
<p>This allows us to see what was actually saved to the database:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">db</span><span class="o">.</span><span class="n">test</span><span class="o">.</span><span class="n">find_one</span><span class="p">()</span>
<span class="go">{u&#39;_id&#39;: ObjectId(&#39;...&#39;), u&#39;custom&#39;: {u&#39;x&#39;: 5, u&#39;_type&#39;: u&#39;custom&#39;}}</span>
</pre></div>
</div>
<p>which is the same format that we encode to with our
<tt class="xref py py-meth docutils literal"><span class="pre">encode_custom()</span></tt> method!</p>
</div>
<div class="section" id="binary-encoding">
<h2>Binary Encoding<a class="headerlink" href="#binary-encoding" title="Permalink to this headline"></a></h2>
<p>We can take this one step further by encoding to binary, using a user
defined subtype. This allows us to identify what to decode without
resorting to tricks like the <tt class="docutils literal"><span class="pre">_type</span></tt> field used above.</p>
<p>We&#8217;ll start by defining the methods <tt class="xref py py-meth docutils literal"><span class="pre">to_binary()</span></tt> and
<tt class="xref py py-meth docutils literal"><span class="pre">from_binary()</span></tt>, which convert <tt class="xref py py-class docutils literal"><span class="pre">Custom</span></tt> instances to and
from <a class="reference internal" href="../api/bson/binary.html#bson.binary.Binary" title="bson.binary.Binary"><tt class="xref py py-class docutils literal"><span class="pre">Binary</span></tt></a> instances:</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">You could just pickle the instance and save that. What we do
here is a little more lightweight.</p>
</div>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="kn">from</span> <span class="nn">bson.binary</span> <span class="kn">import</span> <span class="n">Binary</span>
<span class="gp">&gt;&gt;&gt; </span><span class="k">def</span> <span class="nf">to_binary</span><span class="p">(</span><span class="n">custom</span><span class="p">):</span>
<span class="gp">... </span>  <span class="k">return</span> <span class="n">Binary</span><span class="p">(</span><span class="nb">str</span><span class="p">(</span><span class="n">custom</span><span class="o">.</span><span class="n">x</span><span class="p">()),</span> <span class="mi">128</span><span class="p">)</span>
<span class="gp">...</span>
<span class="gp">&gt;&gt;&gt; </span><span class="k">def</span> <span class="nf">from_binary</span><span class="p">(</span><span class="n">binary</span><span class="p">):</span>
<span class="gp">... </span>  <span class="k">return</span> <span class="n">Custom</span><span class="p">(</span><span class="nb">int</span><span class="p">(</span><span class="n">binary</span><span class="p">))</span>
<span class="gp">...</span>
</pre></div>
</div>
<p>Next we&#8217;ll create another
<a class="reference internal" href="../api/pymongo/son_manipulator.html#pymongo.son_manipulator.SONManipulator" title="pymongo.son_manipulator.SONManipulator"><tt class="xref py py-class docutils literal"><span class="pre">SONManipulator</span></tt></a>, this time using the
methods we just defined:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="k">class</span> <span class="nc">TransformToBinary</span><span class="p">(</span><span class="n">SONManipulator</span><span class="p">):</span>
<span class="gp">... </span>  <span class="k">def</span> <span class="nf">transform_incoming</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">son</span><span class="p">,</span> <span class="n">collection</span><span class="p">):</span>
<span class="gp">... </span>    <span class="k">for</span> <span class="p">(</span><span class="n">key</span><span class="p">,</span> <span class="n">value</span><span class="p">)</span> <span class="ow">in</span> <span class="n">son</span><span class="o">.</span><span class="n">items</span><span class="p">():</span>
<span class="gp">... </span>      <span class="k">if</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">value</span><span class="p">,</span> <span class="n">Custom</span><span class="p">):</span>
<span class="gp">... </span>        <span class="n">son</span><span class="p">[</span><span class="n">key</span><span class="p">]</span> <span class="o">=</span> <span class="n">to_binary</span><span class="p">(</span><span class="n">value</span><span class="p">)</span>
<span class="gp">... </span>      <span class="k">elif</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">value</span><span class="p">,</span> <span class="nb">dict</span><span class="p">):</span>
<span class="gp">... </span>        <span class="n">son</span><span class="p">[</span><span class="n">key</span><span class="p">]</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">transform_incoming</span><span class="p">(</span><span class="n">value</span><span class="p">,</span> <span class="n">collection</span><span class="p">)</span>
<span class="gp">... </span>    <span class="k">return</span> <span class="n">son</span>
<span class="gp">...</span>
<span class="gp">... </span>  <span class="k">def</span> <span class="nf">transform_outgoing</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">son</span><span class="p">,</span> <span class="n">collection</span><span class="p">):</span>
<span class="gp">... </span>    <span class="k">for</span> <span class="p">(</span><span class="n">key</span><span class="p">,</span> <span class="n">value</span><span class="p">)</span> <span class="ow">in</span> <span class="n">son</span><span class="o">.</span><span class="n">items</span><span class="p">():</span>
<span class="gp">... </span>      <span class="k">if</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">value</span><span class="p">,</span> <span class="n">Binary</span><span class="p">)</span> <span class="ow">and</span> <span class="n">value</span><span class="o">.</span><span class="n">subtype</span> <span class="o">==</span> <span class="mi">128</span><span class="p">:</span>
<span class="gp">... </span>        <span class="n">son</span><span class="p">[</span><span class="n">key</span><span class="p">]</span> <span class="o">=</span> <span class="n">from_binary</span><span class="p">(</span><span class="n">value</span><span class="p">)</span>
<span class="gp">... </span>      <span class="k">elif</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">value</span><span class="p">,</span> <span class="nb">dict</span><span class="p">):</span>
<span class="gp">... </span>        <span class="n">son</span><span class="p">[</span><span class="n">key</span><span class="p">]</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">transform_outgoing</span><span class="p">(</span><span class="n">value</span><span class="p">,</span> <span class="n">collection</span><span class="p">)</span>
<span class="gp">... </span>    <span class="k">return</span> <span class="n">son</span>
<span class="gp">...</span>
</pre></div>
</div>
<p>Now we&#8217;ll empty the <a class="reference internal" href="../api/pymongo/database.html#pymongo.database.Database" title="pymongo.database.Database"><tt class="xref py py-class docutils literal"><span class="pre">Database</span></tt></a> and add the
new manipulator:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">db</span><span class="o">.</span><span class="n">test</span><span class="o">.</span><span class="n">remove</span><span class="p">()</span>
<span class="go">{...}</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">db</span><span class="o">.</span><span class="n">add_son_manipulator</span><span class="p">(</span><span class="n">TransformToBinary</span><span class="p">())</span>
</pre></div>
</div>
<p>After doing so we can save and restore <tt class="xref py py-class docutils literal"><span class="pre">Custom</span></tt> instances
seamlessly:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">db</span><span class="o">.</span><span class="n">test</span><span class="o">.</span><span class="n">insert</span><span class="p">({</span><span class="s">&quot;custom&quot;</span><span class="p">:</span> <span class="n">Custom</span><span class="p">(</span><span class="mi">5</span><span class="p">)})</span>
<span class="go">ObjectId(&#39;...&#39;)</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">db</span><span class="o">.</span><span class="n">test</span><span class="o">.</span><span class="n">find_one</span><span class="p">()</span>
<span class="go">{u&#39;_id&#39;: ObjectId(&#39;...&#39;), u&#39;custom&#39;: &lt;Custom object at ...&gt;}</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">db</span><span class="o">.</span><span class="n">test</span><span class="o">.</span><span class="n">find_one</span><span class="p">()[</span><span class="s">&quot;custom&quot;</span><span class="p">]</span><span class="o">.</span><span class="n">x</span><span class="p">()</span>
<span class="go">5</span>
</pre></div>
</div>
<p>We can see what&#8217;s actually being saved to the database (and verify
that it is using a <a class="reference internal" href="../api/bson/binary.html#bson.binary.Binary" title="bson.binary.Binary"><tt class="xref py py-class docutils literal"><span class="pre">Binary</span></tt></a> instance) by
clearing out the manipulators and repeating our
<a class="reference internal" href="../api/pymongo/collection.html#pymongo.collection.Collection.find_one" title="pymongo.collection.Collection.find_one"><tt class="xref py py-meth docutils literal"><span class="pre">find_one()</span></tt></a>:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">db</span> <span class="o">=</span> <span class="n">client</span><span class="o">.</span><span class="n">custom_type_example</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">db</span><span class="o">.</span><span class="n">test</span><span class="o">.</span><span class="n">find_one</span><span class="p">()</span>
<span class="go">{u&#39;_id&#39;: ObjectId(&#39;...&#39;), u&#39;custom&#39;: Binary(&#39;5&#39;, 128)}</span>
</pre></div>
</div>
</div>
</div>


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