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<div class="section" id="gridfs">
<h1>GridFS<a class="headerlink" href="#gridfs" title="Permalink to this headline">¶</a></h1>
<p class="versionadded">
<span class="versionmodified">New in version 0.4.</span></p>
<div class="section" id="writing">
<h2>Writing<a class="headerlink" href="#writing" title="Permalink to this headline">¶</a></h2>
<p>GridFS support comes in the form of the <a class="reference internal" href="../apireference.html#mongoengine.FileField" title="mongoengine.FileField"><tt class="xref py py-class docutils literal"><span class="pre">FileField</span></tt></a> field
object. This field acts as a file-like object and provides a couple of
different ways of inserting and retrieving data. Arbitrary metadata such as
content type can also be stored alongside the files. In the following example,
a document is created to store details about animals, including a photo:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="k">class</span> <span class="nc">Animal</span><span class="p">(</span><span class="n">Document</span><span class="p">):</span>
<span class="n">genus</span> <span class="o">=</span> <span class="n">StringField</span><span class="p">()</span>
<span class="n">family</span> <span class="o">=</span> <span class="n">StringField</span><span class="p">()</span>
<span class="n">photo</span> <span class="o">=</span> <span class="n">FileField</span><span class="p">()</span>
<span class="n">marmot</span> <span class="o">=</span> <span class="n">Animal</span><span class="p">(</span><span class="s">'Marmota'</span><span class="p">,</span> <span class="s">'Sciuridae'</span><span class="p">)</span>
<span class="n">marmot_photo</span> <span class="o">=</span> <span class="nb">open</span><span class="p">(</span><span class="s">'marmot.jpg'</span><span class="p">,</span> <span class="s">'r'</span><span class="p">)</span> <span class="c"># Retrieve a photo from disk</span>
<span class="n">marmot</span><span class="o">.</span><span class="n">photo</span> <span class="o">=</span> <span class="n">marmot_photo</span> <span class="c"># Store photo in the document</span>
<span class="n">marmot</span><span class="o">.</span><span class="n">photo</span><span class="o">.</span><span class="n">content_type</span> <span class="o">=</span> <span class="s">'image/jpeg'</span> <span class="c"># Store metadata</span>
<span class="n">marmot</span><span class="o">.</span><span class="n">save</span><span class="p">()</span>
</pre></div>
</div>
<p>Another way of writing to a <a class="reference internal" href="../apireference.html#mongoengine.FileField" title="mongoengine.FileField"><tt class="xref py py-class docutils literal"><span class="pre">FileField</span></tt></a> is to use the
<tt class="xref py py-func docutils literal"><span class="pre">put()</span></tt> method. This allows for metadata to be stored in the same call as
the file:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">marmot</span><span class="o">.</span><span class="n">photo</span><span class="o">.</span><span class="n">put</span><span class="p">(</span><span class="n">marmot_photo</span><span class="p">,</span> <span class="n">content_type</span><span class="o">=</span><span class="s">'image/jpeg'</span><span class="p">)</span>
<span class="n">marmot</span><span class="o">.</span><span class="n">save</span><span class="p">()</span>
</pre></div>
</div>
</div>
<div class="section" id="retrieval">
<h2>Retrieval<a class="headerlink" href="#retrieval" title="Permalink to this headline">¶</a></h2>
<p>So using the <a class="reference internal" href="../apireference.html#mongoengine.FileField" title="mongoengine.FileField"><tt class="xref py py-class docutils literal"><span class="pre">FileField</span></tt></a> is just like using any other
field. The file can also be retrieved just as easily:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">marmot</span> <span class="o">=</span> <span class="n">Animal</span><span class="o">.</span><span class="n">objects</span><span class="p">(</span><span class="n">genus</span><span class="o">=</span><span class="s">'Marmota'</span><span class="p">)</span><span class="o">.</span><span class="n">first</span><span class="p">()</span>
<span class="n">photo</span> <span class="o">=</span> <span class="n">marmot</span><span class="o">.</span><span class="n">photo</span><span class="o">.</span><span class="n">read</span><span class="p">()</span>
<span class="n">content_type</span> <span class="o">=</span> <span class="n">marmot</span><span class="o">.</span><span class="n">photo</span><span class="o">.</span><span class="n">content_type</span>
</pre></div>
</div>
</div>
<div class="section" id="streaming">
<h2>Streaming<a class="headerlink" href="#streaming" title="Permalink to this headline">¶</a></h2>
<p>Streaming data into a <a class="reference internal" href="../apireference.html#mongoengine.FileField" title="mongoengine.FileField"><tt class="xref py py-class docutils literal"><span class="pre">FileField</span></tt></a> is achieved in a
slightly different manner. First, a new file must be created by calling the
<tt class="xref py py-func docutils literal"><span class="pre">new_file()</span></tt> method. Data can then be written using <tt class="xref py py-func docutils literal"><span class="pre">write()</span></tt>:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">marmot</span><span class="o">.</span><span class="n">photo</span><span class="o">.</span><span class="n">new_file</span><span class="p">()</span>
<span class="n">marmot</span><span class="o">.</span><span class="n">photo</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="s">'some_image_data'</span><span class="p">)</span>
<span class="n">marmot</span><span class="o">.</span><span class="n">photo</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="s">'some_more_image_data'</span><span class="p">)</span>
<span class="n">marmot</span><span class="o">.</span><span class="n">photo</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
<span class="n">marmot</span><span class="o">.</span><span class="n">photo</span><span class="o">.</span><span class="n">save</span><span class="p">()</span>
</pre></div>
</div>
</div>
<div class="section" id="deletion">
<h2>Deletion<a class="headerlink" href="#deletion" title="Permalink to this headline">¶</a></h2>
<p>Deleting stored files is achieved with the <tt class="xref py py-func docutils literal"><span class="pre">delete()</span></tt> method:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">marmot</span><span class="o">.</span><span class="n">photo</span><span class="o">.</span><span class="n">delete</span><span class="p">()</span>
</pre></div>
</div>
<div class="admonition warning">
<p class="first admonition-title">Warning</p>
<p class="last">The FileField in a Document actually only stores the ID of a file in a
separate GridFS collection. This means that deleting a document
with a defined FileField does not actually delete the file. You must be
careful to delete any files in a Document as above before deleting the
Document itself.</p>
</div>
</div>
<div class="section" id="replacing-files">
<h2>Replacing files<a class="headerlink" href="#replacing-files" title="Permalink to this headline">¶</a></h2>
<p>Files can be replaced with the <tt class="xref py py-func docutils literal"><span class="pre">replace()</span></tt> method. This works just like
the <tt class="xref py py-func docutils literal"><span class="pre">put()</span></tt> method so even metadata can (and should) be replaced:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">another_marmot</span> <span class="o">=</span> <span class="nb">open</span><span class="p">(</span><span class="s">'another_marmot.png'</span><span class="p">,</span> <span class="s">'r'</span><span class="p">)</span>
<span class="n">marmot</span><span class="o">.</span><span class="n">photo</span><span class="o">.</span><span class="n">replace</span><span class="p">(</span><span class="n">another_marmot</span><span class="p">,</span> <span class="n">content_type</span><span class="o">=</span><span class="s">'image/png'</span><span class="p">)</span>
</pre></div>
</div>
</div>
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<h3><a href="../index.html">Table Of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#">GridFS</a><ul>
<li><a class="reference internal" href="#writing">Writing</a></li>
<li><a class="reference internal" href="#retrieval">Retrieval</a></li>
<li><a class="reference internal" href="#streaming">Streaming</a></li>
<li><a class="reference internal" href="#deletion">Deletion</a></li>
<li><a class="reference internal" href="#replacing-files">Replacing files</a></li>
</ul>
</li>
</ul>
<h4>Previous topic</h4>
<p class="topless"><a href="querying.html"
title="previous chapter">Querying the database</a></p>
<h4>Next topic</h4>
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title="next chapter">Signals</a></p>
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