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examples.graphs.directed_graph
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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.graphs.directed_graph</h1><div class="highlight"><pre>
<span class="sd">"""a directed graph 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">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="kn">from</span> <span class="nn">sqlalchemy.ext.declarative</span> <span class="kn">import</span> <span class="n">declarative_base</span>
<span class="n">Base</span> <span class="o">=</span> <span class="n">declarative_base</span><span class="p">()</span>
<span class="k">class</span> <span class="nc">Node</span><span class="p">(</span><span class="n">Base</span><span class="p">):</span>
<span class="n">__tablename__</span> <span class="o">=</span> <span class="s">'node'</span>
<span class="n">node_id</span> <span class="o">=</span> <span class="n">Column</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="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="nb">id</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">node_id</span> <span class="o">=</span> <span class="nb">id</span>
<span class="k">def</span> <span class="nf">add_neighbors</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="o">*</span><span class="n">nodes</span><span class="p">):</span>
<span class="k">for</span> <span class="n">node</span> <span class="ow">in</span> <span class="n">nodes</span><span class="p">:</span>
<span class="n">Edge</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">node</span><span class="p">)</span>
<span class="k">return</span> <span class="bp">self</span>
<span class="k">def</span> <span class="nf">higher_neighbors</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="k">return</span> <span class="p">[</span><span class="n">x</span><span class="o">.</span><span class="n">higher_node</span> <span class="k">for</span> <span class="n">x</span> <span class="ow">in</span> <span class="bp">self</span><span class="o">.</span><span class="n">lower_edges</span><span class="p">]</span>
<span class="k">def</span> <span class="nf">lower_neighbors</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="k">return</span> <span class="p">[</span><span class="n">x</span><span class="o">.</span><span class="n">lower_node</span> <span class="k">for</span> <span class="n">x</span> <span class="ow">in</span> <span class="bp">self</span><span class="o">.</span><span class="n">higher_edges</span><span class="p">]</span>
<span class="k">class</span> <span class="nc">Edge</span><span class="p">(</span><span class="n">Base</span><span class="p">):</span>
<span class="n">__tablename__</span> <span class="o">=</span> <span class="s">'edge'</span>
<span class="n">lower_id</span> <span class="o">=</span> <span class="n">Column</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">'node.node_id'</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">higher_id</span> <span class="o">=</span> <span class="n">Column</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">'node.node_id'</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">lower_node</span> <span class="o">=</span> <span class="n">relationship</span><span class="p">(</span><span class="n">Node</span><span class="p">,</span>
<span class="n">primaryjoin</span><span class="o">=</span><span class="n">lower_id</span><span class="o">==</span><span class="n">Node</span><span class="o">.</span><span class="n">node_id</span><span class="p">,</span>
<span class="n">backref</span><span class="o">=</span><span class="s">'lower_edges'</span><span class="p">)</span>
<span class="n">higher_node</span> <span class="o">=</span> <span class="n">relationship</span><span class="p">(</span><span class="n">Node</span><span class="p">,</span>
<span class="n">primaryjoin</span><span class="o">=</span><span class="n">higher_id</span><span class="o">==</span><span class="n">Node</span><span class="o">.</span><span class="n">node_id</span><span class="p">,</span>
<span class="n">backref</span><span class="o">=</span><span class="s">'higher_edges'</span><span class="p">)</span>
<span class="c"># here we have lower.node_id <= higher.node_id</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">n1</span><span class="p">,</span> <span class="n">n2</span><span class="p">):</span>
<span class="k">if</span> <span class="n">n1</span><span class="o">.</span><span class="n">node_id</span> <span class="o"><</span> <span class="n">n2</span><span class="o">.</span><span class="n">node_id</span><span class="p">:</span>
<span class="bp">self</span><span class="o">.</span><span class="n">lower_node</span> <span class="o">=</span> <span class="n">n1</span>
<span class="bp">self</span><span class="o">.</span><span class="n">higher_node</span> <span class="o">=</span> <span class="n">n2</span>
<span class="k">else</span><span class="p">:</span>
<span class="bp">self</span><span class="o">.</span><span class="n">lower_node</span> <span class="o">=</span> <span class="n">n2</span>
<span class="bp">self</span><span class="o">.</span><span class="n">higher_node</span> <span class="o">=</span> <span class="n">n1</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">Base</span><span class="o">.</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="c"># create a directed graph like this:</span>
<span class="c"># n1 -> n2 -> n5</span>
<span class="c"># -> n7</span>
<span class="c"># -> n3 -> n6</span>
<span class="n">n1</span> <span class="o">=</span> <span class="n">Node</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span>
<span class="n">n2</span> <span class="o">=</span> <span class="n">Node</span><span class="p">(</span><span class="mi">2</span><span class="p">)</span>
<span class="n">n3</span> <span class="o">=</span> <span class="n">Node</span><span class="p">(</span><span class="mi">3</span><span class="p">)</span>
<span class="n">n4</span> <span class="o">=</span> <span class="n">Node</span><span class="p">(</span><span class="mi">4</span><span class="p">)</span>
<span class="n">n5</span> <span class="o">=</span> <span class="n">Node</span><span class="p">(</span><span class="mi">5</span><span class="p">)</span>
<span class="n">n6</span> <span class="o">=</span> <span class="n">Node</span><span class="p">(</span><span class="mi">6</span><span class="p">)</span>
<span class="n">n7</span> <span class="o">=</span> <span class="n">Node</span><span class="p">(</span><span class="mi">7</span><span class="p">)</span>
<span class="n">n2</span><span class="o">.</span><span class="n">add_neighbors</span><span class="p">(</span><span class="n">n5</span><span class="p">,</span> <span class="n">n1</span><span class="p">)</span>
<span class="n">n3</span><span class="o">.</span><span class="n">add_neighbors</span><span class="p">(</span><span class="n">n6</span><span class="p">)</span>
<span class="n">n7</span><span class="o">.</span><span class="n">add_neighbors</span><span class="p">(</span><span class="n">n2</span><span class="p">)</span>
<span class="n">n1</span><span class="o">.</span><span class="n">add_neighbors</span><span class="p">(</span><span class="n">n3</span><span class="p">)</span>
<span class="n">session</span><span class="o">.</span><span class="n">add_all</span><span class="p">([</span><span class="n">n1</span><span class="p">,</span> <span class="n">n2</span><span class="p">,</span> <span class="n">n3</span><span class="p">,</span> <span class="n">n4</span><span class="p">,</span> <span class="n">n5</span><span class="p">,</span> <span class="n">n6</span><span class="p">,</span> <span class="n">n7</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="k">assert</span> <span class="p">[</span><span class="n">x</span><span class="o">.</span><span class="n">node_id</span> <span class="k">for</span> <span class="n">x</span> <span class="ow">in</span> <span class="n">n3</span><span class="o">.</span><span class="n">higher_neighbors</span><span class="p">()]</span> <span class="o">==</span> <span class="p">[</span><span class="mi">6</span><span class="p">]</span>
<span class="k">assert</span> <span class="p">[</span><span class="n">x</span><span class="o">.</span><span class="n">node_id</span> <span class="k">for</span> <span class="n">x</span> <span class="ow">in</span> <span class="n">n3</span><span class="o">.</span><span class="n">lower_neighbors</span><span class="p">()]</span> <span class="o">==</span> <span class="p">[</span><span class="mi">1</span><span class="p">]</span>
<span class="k">assert</span> <span class="p">[</span><span class="n">x</span><span class="o">.</span><span class="n">node_id</span> <span class="k">for</span> <span class="n">x</span> <span class="ow">in</span> <span class="n">n2</span><span class="o">.</span><span class="n">lower_neighbors</span><span class="p">()]</span> <span class="o">==</span> <span class="p">[</span><span class="mi">1</span><span class="p">]</span>
<span class="k">assert</span> <span class="p">[</span><span class="n">x</span><span class="o">.</span><span class="n">node_id</span> <span class="k">for</span> <span class="n">x</span> <span class="ow">in</span> <span class="n">n2</span><span class="o">.</span><span class="n">higher_neighbors</span><span class="p">()]</span> <span class="o">==</span> <span class="p">[</span><span class="mi">5</span><span class="p">,</span><span class="mi">7</span><span class="p">]</span></pre></div>
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