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        Release: <span class="version-num">0.9.8</span> | Release Date: October 13, 2014
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    <h1>SQLAlchemy 0.9 Documentation</h1>

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<h1>Source code for examples.elementtree.pickle</h1><div class="highlight"><pre>
<span class="sd">&quot;&quot;&quot;illustrates a quick and dirty way to persist an XML document expressed using ElementTree and pickle.</span>

<span class="sd">This is a trivial example using PickleType to marshal/unmarshal the ElementTree</span>
<span class="sd">document into a binary column.  Compare to explicit.py which stores the individual components of the ElementTree</span>
<span class="sd">structure in distinct rows using two additional mapped entities.  Note that the usage of both</span>
<span class="sd">styles of persistence are identical, as is the structure of the main Document class.</span>
<span class="sd">&quot;&quot;&quot;</span>

<span class="kn">from</span> <span class="nn">sqlalchemy</span> <span class="kn">import</span> <span class="p">(</span><span class="n">create_engine</span><span class="p">,</span> <span class="n">MetaData</span><span class="p">,</span> <span class="n">Table</span><span class="p">,</span> <span class="n">Column</span><span class="p">,</span> <span class="n">Integer</span><span class="p">,</span> <span class="n">String</span><span class="p">,</span>
    <span class="n">PickleType</span><span class="p">)</span>
<span class="kn">from</span> <span class="nn">sqlalchemy.orm</span> <span class="kn">import</span> <span class="n">mapper</span><span class="p">,</span> <span class="n">Session</span>

<span class="kn">import</span> <span class="nn">sys</span><span class="o">,</span> <span class="nn">os</span>

<span class="kn">from</span> <span class="nn">xml.etree</span> <span class="kn">import</span> <span class="n">ElementTree</span>

<span class="n">e</span> <span class="o">=</span> <span class="n">create_engine</span><span class="p">(</span><span class="s">&#39;sqlite://&#39;</span><span class="p">)</span>
<span class="n">meta</span> <span class="o">=</span> <span class="n">MetaData</span><span class="p">()</span>

<span class="c"># setup a comparator for the PickleType since it&#39;s a mutable</span>
<span class="c"># element.</span>
<span class="k">def</span> <span class="nf">are_elements_equal</span><span class="p">(</span><span class="n">x</span><span class="p">,</span> <span class="n">y</span><span class="p">):</span>
    <span class="k">return</span> <span class="n">x</span> <span class="o">==</span> <span class="n">y</span>

<span class="c"># stores a top level record of an XML document.</span>
<span class="c"># the &quot;element&quot; column will store the ElementTree document as a BLOB.</span>
<span class="n">documents</span> <span class="o">=</span> <span class="n">Table</span><span class="p">(</span><span class="s">&#39;documents&#39;</span><span class="p">,</span> <span class="n">meta</span><span class="p">,</span>
    <span class="n">Column</span><span class="p">(</span><span class="s">&#39;document_id&#39;</span><span class="p">,</span> <span class="n">Integer</span><span class="p">,</span> <span class="n">primary_key</span><span class="o">=</span><span class="bp">True</span><span class="p">),</span>
    <span class="n">Column</span><span class="p">(</span><span class="s">&#39;filename&#39;</span><span class="p">,</span> <span class="n">String</span><span class="p">(</span><span class="mi">30</span><span class="p">),</span> <span class="n">unique</span><span class="o">=</span><span class="bp">True</span><span class="p">),</span>
    <span class="n">Column</span><span class="p">(</span><span class="s">&#39;element&#39;</span><span class="p">,</span> <span class="n">PickleType</span><span class="p">(</span><span class="n">comparator</span><span class="o">=</span><span class="n">are_elements_equal</span><span class="p">))</span>
<span class="p">)</span>

<span class="n">meta</span><span class="o">.</span><span class="n">create_all</span><span class="p">(</span><span class="n">e</span><span class="p">)</span>

<span class="c"># our document class.  contains a string name,</span>
<span class="c"># and the ElementTree root element.</span>
<span class="k">class</span> <span class="nc">Document</span><span class="p">(</span><span class="nb">object</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">name</span><span class="p">,</span> <span class="n">element</span><span class="p">):</span>
        <span class="bp">self</span><span class="o">.</span><span class="n">filename</span> <span class="o">=</span> <span class="n">name</span>
        <span class="bp">self</span><span class="o">.</span><span class="n">element</span> <span class="o">=</span> <span class="n">element</span>

<span class="c"># setup mapper.</span>
<span class="n">mapper</span><span class="p">(</span><span class="n">Document</span><span class="p">,</span> <span class="n">documents</span><span class="p">)</span>

<span class="c">###### time to test ! #########</span>

<span class="c"># get ElementTree document</span>
<span class="n">filename</span> <span class="o">=</span> <span class="n">os</span><span class="o">.</span><span class="n">path</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="n">os</span><span class="o">.</span><span class="n">path</span><span class="o">.</span><span class="n">dirname</span><span class="p">(</span><span class="n">__file__</span><span class="p">),</span> <span class="s">&quot;test.xml&quot;</span><span class="p">)</span>
<span class="n">doc</span> <span class="o">=</span> <span class="n">ElementTree</span><span class="o">.</span><span class="n">parse</span><span class="p">(</span><span class="n">filename</span><span class="p">)</span>

<span class="c"># save to DB</span>
<span class="n">session</span> <span class="o">=</span> <span class="n">Session</span><span class="p">(</span><span class="n">e</span><span class="p">)</span>
<span class="n">session</span><span class="o">.</span><span class="n">add</span><span class="p">(</span><span class="n">Document</span><span class="p">(</span><span class="s">&quot;test.xml&quot;</span><span class="p">,</span> <span class="n">doc</span><span class="p">))</span>
<span class="n">session</span><span class="o">.</span><span class="n">commit</span><span class="p">()</span>

<span class="c"># restore</span>
<span class="n">document</span> <span class="o">=</span> <span class="n">session</span><span class="o">.</span><span class="n">query</span><span class="p">(</span><span class="n">Document</span><span class="p">)</span><span class="o">.</span><span class="n">filter_by</span><span class="p">(</span><span class="n">filename</span><span class="o">=</span><span class="s">&quot;test.xml&quot;</span><span class="p">)</span><span class="o">.</span><span class="n">first</span><span class="p">()</span>

<span class="c"># print</span>
<span class="n">document</span><span class="o">.</span><span class="n">element</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="n">sys</span><span class="o">.</span><span class="n">stdout</span><span class="p">)</span></pre></div>
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