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SQLAlchemy 0.9 Documentation
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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.inheritance.single</h1><div class="highlight"><pre>
<span class="sd">"""Single-table inheritance example."""</span>
<span class="kn">from</span> <span class="nn">sqlalchemy</span> <span class="kn">import</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">ForeignKey</span><span class="p">,</span> <span class="n">create_engine</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">relationship</span><span class="p">,</span> <span class="n">sessionmaker</span>
<span class="n">metadata</span> <span class="o">=</span> <span class="n">MetaData</span><span class="p">()</span>
<span class="c"># a table to store companies</span>
<span class="n">companies</span> <span class="o">=</span> <span class="n">Table</span><span class="p">(</span><span class="s">'companies'</span><span class="p">,</span> <span class="n">metadata</span><span class="p">,</span>
<span class="n">Column</span><span class="p">(</span><span class="s">'company_id'</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">'name'</span><span class="p">,</span> <span class="n">String</span><span class="p">(</span><span class="mi">50</span><span class="p">)))</span>
<span class="n">employees_table</span> <span class="o">=</span> <span class="n">Table</span><span class="p">(</span><span class="s">'employees'</span><span class="p">,</span> <span class="n">metadata</span><span class="p">,</span>
<span class="n">Column</span><span class="p">(</span><span class="s">'employee_id'</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">'company_id'</span><span class="p">,</span> <span class="n">Integer</span><span class="p">,</span> <span class="n">ForeignKey</span><span class="p">(</span><span class="s">'companies.company_id'</span><span class="p">)),</span>
<span class="n">Column</span><span class="p">(</span><span class="s">'name'</span><span class="p">,</span> <span class="n">String</span><span class="p">(</span><span class="mi">50</span><span class="p">)),</span>
<span class="n">Column</span><span class="p">(</span><span class="s">'type'</span><span class="p">,</span> <span class="n">String</span><span class="p">(</span><span class="mi">20</span><span class="p">)),</span>
<span class="n">Column</span><span class="p">(</span><span class="s">'status'</span><span class="p">,</span> <span class="n">String</span><span class="p">(</span><span class="mi">20</span><span class="p">)),</span>
<span class="n">Column</span><span class="p">(</span><span class="s">'engineer_name'</span><span class="p">,</span> <span class="n">String</span><span class="p">(</span><span class="mi">50</span><span class="p">)),</span>
<span class="n">Column</span><span class="p">(</span><span class="s">'primary_language'</span><span class="p">,</span> <span class="n">String</span><span class="p">(</span><span class="mi">50</span><span class="p">)),</span>
<span class="n">Column</span><span class="p">(</span><span class="s">'manager_name'</span><span class="p">,</span> <span class="n">String</span><span class="p">(</span><span class="mi">50</span><span class="p">))</span>
<span class="p">)</span>
<span class="k">class</span> <span class="nc">Person</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="o">**</span><span class="n">kwargs</span><span class="p">):</span>
<span class="k">for</span> <span class="n">key</span><span class="p">,</span> <span class="n">value</span> <span class="ow">in</span> <span class="n">kwargs</span><span class="o">.</span><span class="n">items</span><span class="p">():</span>
<span class="nb">setattr</span><span class="p">(</span><span class="bp">self</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="k">def</span> <span class="nf">__repr__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="k">return</span> <span class="s">"Ordinary person </span><span class="si">%s</span><span class="s">"</span> <span class="o">%</span> <span class="bp">self</span><span class="o">.</span><span class="n">name</span>
<span class="k">class</span> <span class="nc">Engineer</span><span class="p">(</span><span class="n">Person</span><span class="p">):</span>
<span class="k">def</span> <span class="nf">__repr__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="k">return</span> <span class="s">"Engineer </span><span class="si">%s</span><span class="s">, status </span><span class="si">%s</span><span class="s">, engineer_name </span><span class="si">%s</span><span class="s">, "</span>\
<span class="s">"primary_language </span><span class="si">%s</span><span class="s">"</span> <span class="o">%</span> \
<span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">name</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">status</span><span class="p">,</span>
<span class="bp">self</span><span class="o">.</span><span class="n">engineer_name</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">primary_language</span><span class="p">)</span>
<span class="k">class</span> <span class="nc">Manager</span><span class="p">(</span><span class="n">Person</span><span class="p">):</span>
<span class="k">def</span> <span class="nf">__repr__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="k">return</span> <span class="s">"Manager </span><span class="si">%s</span><span class="s">, status </span><span class="si">%s</span><span class="s">, manager_name </span><span class="si">%s</span><span class="s">"</span> <span class="o">%</span> \
<span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">name</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">status</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">manager_name</span><span class="p">)</span>
<span class="k">class</span> <span class="nc">Company</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="o">**</span><span class="n">kwargs</span><span class="p">):</span>
<span class="k">for</span> <span class="n">key</span><span class="p">,</span> <span class="n">value</span> <span class="ow">in</span> <span class="n">kwargs</span><span class="o">.</span><span class="n">items</span><span class="p">():</span>
<span class="nb">setattr</span><span class="p">(</span><span class="bp">self</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="k">def</span> <span class="nf">__repr__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="k">return</span> <span class="s">"Company </span><span class="si">%s</span><span class="s">"</span> <span class="o">%</span> <span class="bp">self</span><span class="o">.</span><span class="n">name</span>
<span class="n">person_mapper</span> <span class="o">=</span> <span class="n">mapper</span><span class="p">(</span><span class="n">Person</span><span class="p">,</span> <span class="n">employees_table</span><span class="p">,</span>
<span class="n">polymorphic_on</span><span class="o">=</span><span class="n">employees_table</span><span class="o">.</span><span class="n">c</span><span class="o">.</span><span class="n">type</span><span class="p">,</span>
<span class="n">polymorphic_identity</span><span class="o">=</span><span class="s">'person'</span><span class="p">)</span>
<span class="n">manager_mapper</span> <span class="o">=</span> <span class="n">mapper</span><span class="p">(</span><span class="n">Manager</span><span class="p">,</span> <span class="n">inherits</span><span class="o">=</span><span class="n">person_mapper</span><span class="p">,</span>
<span class="n">polymorphic_identity</span><span class="o">=</span><span class="s">'manager'</span><span class="p">)</span>
<span class="n">engineer_mapper</span> <span class="o">=</span> <span class="n">mapper</span><span class="p">(</span><span class="n">Engineer</span><span class="p">,</span> <span class="n">inherits</span><span class="o">=</span><span class="n">person_mapper</span><span class="p">,</span>
<span class="n">polymorphic_identity</span><span class="o">=</span><span class="s">'engineer'</span><span class="p">)</span>
<span class="n">mapper</span><span class="p">(</span><span class="n">Company</span><span class="p">,</span> <span class="n">companies</span><span class="p">,</span> <span class="n">properties</span><span class="o">=</span><span class="p">{</span>
<span class="s">'employees'</span><span class="p">:</span> <span class="n">relationship</span><span class="p">(</span><span class="n">Person</span><span class="p">,</span> <span class="n">lazy</span><span class="o">=</span><span class="bp">True</span><span class="p">,</span> <span class="n">backref</span><span class="o">=</span><span class="s">'company'</span><span class="p">)</span>
<span class="p">})</span>
<span class="n">engine</span> <span class="o">=</span> <span class="n">create_engine</span><span class="p">(</span><span class="s">'sqlite:///'</span><span class="p">,</span> <span class="n">echo</span><span class="o">=</span><span class="bp">True</span><span class="p">)</span>
<span class="n">metadata</span><span class="o">.</span><span class="n">create_all</span><span class="p">(</span><span class="n">engine</span><span class="p">)</span>
<span class="n">session</span> <span class="o">=</span> <span class="n">sessionmaker</span><span class="p">(</span><span class="n">engine</span><span class="p">)()</span>
<span class="n">c</span> <span class="o">=</span> <span class="n">Company</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s">'company1'</span><span class="p">)</span>
<span class="n">c</span><span class="o">.</span><span class="n">employees</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">Manager</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s">'pointy haired boss'</span><span class="p">,</span> <span class="n">status</span><span class="o">=</span><span class="s">'AAB'</span><span class="p">,</span>
<span class="n">manager_name</span><span class="o">=</span><span class="s">'manager1'</span><span class="p">))</span>
<span class="n">c</span><span class="o">.</span><span class="n">employees</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">Engineer</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s">'dilbert'</span><span class="p">,</span> <span class="n">status</span><span class="o">=</span><span class="s">'BBA'</span><span class="p">,</span>
<span class="n">engineer_name</span><span class="o">=</span><span class="s">'engineer1'</span><span class="p">,</span> <span class="n">primary_language</span><span class="o">=</span><span class="s">'java'</span><span class="p">))</span>
<span class="n">c</span><span class="o">.</span><span class="n">employees</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">Person</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s">'joesmith'</span><span class="p">,</span> <span class="n">status</span><span class="o">=</span><span class="s">'HHH'</span><span class="p">))</span>
<span class="n">c</span><span class="o">.</span><span class="n">employees</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">Engineer</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s">'wally'</span><span class="p">,</span> <span class="n">status</span><span class="o">=</span><span class="s">'CGG'</span><span class="p">,</span>
<span class="n">engineer_name</span><span class="o">=</span><span class="s">'engineer2'</span><span class="p">,</span> <span class="n">primary_language</span><span class="o">=</span><span class="s">'python'</span>
<span class="p">))</span>
<span class="n">c</span><span class="o">.</span><span class="n">employees</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">Manager</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s">'jsmith'</span><span class="p">,</span> <span class="n">status</span><span class="o">=</span><span class="s">'ABA'</span><span class="p">,</span>
<span class="n">manager_name</span><span class="o">=</span><span class="s">'manager2'</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">c</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="n">c</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">Company</span><span class="p">)</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span>
<span class="k">for</span> <span class="n">e</span> <span class="ow">in</span> <span class="n">c</span><span class="o">.</span><span class="n">employees</span><span class="p">:</span>
<span class="k">print</span><span class="p">(</span><span class="n">e</span><span class="p">,</span> <span class="n">e</span><span class="o">.</span><span class="n">company</span><span class="p">)</span>
<span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="se">\n</span><span class="s">"</span><span class="p">)</span>
<span class="n">dilbert</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">Person</span><span class="p">)</span><span class="o">.</span><span class="n">filter_by</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s">'dilbert'</span><span class="p">)</span><span class="o">.</span><span class="n">one</span><span class="p">()</span>
<span class="n">dilbert2</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">Engineer</span><span class="p">)</span><span class="o">.</span><span class="n">filter_by</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s">'dilbert'</span><span class="p">)</span><span class="o">.</span><span class="n">one</span><span class="p">()</span>
<span class="k">assert</span> <span class="n">dilbert</span> <span class="ow">is</span> <span class="n">dilbert2</span>
<span class="n">dilbert</span><span class="o">.</span><span class="n">engineer_name</span> <span class="o">=</span> <span class="s">'hes dibert!'</span>
<span class="n">session</span><span class="o">.</span><span class="n">flush</span><span class="p">()</span>
<span class="n">session</span><span class="o">.</span><span class="n">expunge_all</span><span class="p">()</span>
<span class="n">c</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">Company</span><span class="p">)</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span>
<span class="k">for</span> <span class="n">e</span> <span class="ow">in</span> <span class="n">c</span><span class="o">.</span><span class="n">employees</span><span class="p">:</span>
<span class="k">print</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">delete</span><span class="p">(</span><span class="n">c</span><span class="p">)</span>
<span class="n">session</span><span class="o">.</span><span class="n">commit</span><span class="p">()</span></pre></div>
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