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<h1>Source code for networkx.algorithms.components.weakly_connected</h1><div class="highlight"><pre>
<span class="c"># -*- coding: utf-8 -*-</span>
<span class="sd">"""</span>
<span class="sd">Weakly connected components.</span>
<span class="sd">"""</span>
<span class="n">__authors__</span> <span class="o">=</span> <span class="s">"</span><span class="se">\n</span><span class="s">"</span><span class="o">.</span><span class="n">join</span><span class="p">([</span><span class="s">'Aric Hagberg (hagberg@lanl.gov)'</span>
<span class="s">'Christopher Ellison'</span><span class="p">])</span>
<span class="c"># Copyright (C) 2004-2010 by </span>
<span class="c"># Aric Hagberg <hagberg@lanl.gov></span>
<span class="c"># Dan Schult <dschult@colgate.edu></span>
<span class="c"># Pieter Swart <swart@lanl.gov></span>
<span class="c"># All rights reserved.</span>
<span class="c"># BSD license.</span>
<span class="n">__all__</span> <span class="o">=</span> <span class="p">[</span><span class="s">'number_weakly_connected_components'</span><span class="p">,</span>
<span class="s">'weakly_connected_components'</span><span class="p">,</span>
<span class="s">'weakly_connected_component_subgraphs'</span><span class="p">,</span>
<span class="s">'is_weakly_connected'</span>
<span class="p">]</span>
<span class="kn">import</span> <span class="nn">networkx</span> <span class="kn">as</span> <span class="nn">nx</span>
<div class="viewcode-block" id="weakly_connected_components"><a class="viewcode-back" href="../../../../reference/generated/networkx.algorithms.components.weakly_connected.weakly_connected_components.html#networkx.algorithms.components.weakly_connected.weakly_connected_components">[docs]</a><span class="k">def</span> <span class="nf">weakly_connected_components</span><span class="p">(</span><span class="n">G</span><span class="p">):</span>
<span class="sd">"""Return weakly connected components of G.</span>
<span class="sd"> """</span>
<span class="k">if</span> <span class="ow">not</span> <span class="n">G</span><span class="o">.</span><span class="n">is_directed</span><span class="p">():</span>
<span class="k">raise</span> <span class="n">nx</span><span class="o">.</span><span class="n">NetworkXError</span><span class="p">(</span><span class="s">"""Not allowed for undirected graph G. </span>
<span class="s"> Use connected_components() """</span><span class="p">)</span>
<span class="n">seen</span><span class="o">=</span><span class="p">{}</span>
<span class="n">components</span><span class="o">=</span><span class="p">[]</span>
<span class="k">for</span> <span class="n">v</span> <span class="ow">in</span> <span class="n">G</span><span class="p">:</span>
<span class="k">if</span> <span class="n">v</span> <span class="ow">not</span> <span class="ow">in</span> <span class="n">seen</span><span class="p">:</span>
<span class="n">c</span><span class="o">=</span><span class="n">_single_source_shortest_unipath_length</span><span class="p">(</span><span class="n">G</span><span class="p">,</span><span class="n">v</span><span class="p">)</span>
<span class="n">components</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="nb">list</span><span class="p">(</span><span class="n">c</span><span class="o">.</span><span class="n">keys</span><span class="p">()))</span>
<span class="n">seen</span><span class="o">.</span><span class="n">update</span><span class="p">(</span><span class="n">c</span><span class="p">)</span>
<span class="n">components</span><span class="o">.</span><span class="n">sort</span><span class="p">(</span><span class="n">key</span><span class="o">=</span><span class="nb">len</span><span class="p">,</span><span class="n">reverse</span><span class="o">=</span><span class="bp">True</span><span class="p">)</span>
<span class="k">return</span> <span class="n">components</span>
</div>
<div class="viewcode-block" id="number_weakly_connected_components"><a class="viewcode-back" href="../../../../reference/generated/networkx.algorithms.components.weakly_connected.number_weakly_connected_components.html#networkx.algorithms.components.weakly_connected.number_weakly_connected_components">[docs]</a><span class="k">def</span> <span class="nf">number_weakly_connected_components</span><span class="p">(</span><span class="n">G</span><span class="p">):</span>
<span class="sd">"""Return the number of connected components in G.</span>
<span class="sd"> For directed graphs only. </span>
<span class="sd"> """</span>
<span class="k">return</span> <span class="nb">len</span><span class="p">(</span><span class="n">weakly_connected_components</span><span class="p">(</span><span class="n">G</span><span class="p">))</span>
</div>
<div class="viewcode-block" id="weakly_connected_component_subgraphs"><a class="viewcode-back" href="../../../../reference/generated/networkx.algorithms.components.weakly_connected.weakly_connected_component_subgraphs.html#networkx.algorithms.components.weakly_connected.weakly_connected_component_subgraphs">[docs]</a><span class="k">def</span> <span class="nf">weakly_connected_component_subgraphs</span><span class="p">(</span><span class="n">G</span><span class="p">):</span>
<span class="sd">"""Return weakly connected components as subgraphs.</span>
<span class="sd"> Graph, node, and edge attributes are copied to the subgraphs.</span>
<span class="sd"> """</span>
<span class="n">wcc</span><span class="o">=</span><span class="n">weakly_connected_components</span><span class="p">(</span><span class="n">G</span><span class="p">)</span>
<span class="n">graph_list</span><span class="o">=</span><span class="p">[]</span>
<span class="k">for</span> <span class="n">c</span> <span class="ow">in</span> <span class="n">wcc</span><span class="p">:</span>
<span class="n">graph_list</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">G</span><span class="o">.</span><span class="n">subgraph</span><span class="p">(</span><span class="n">c</span><span class="p">)</span><span class="o">.</span><span class="n">copy</span><span class="p">())</span>
<span class="k">return</span> <span class="n">graph_list</span>
</div>
<div class="viewcode-block" id="is_weakly_connected"><a class="viewcode-back" href="../../../../reference/generated/networkx.algorithms.components.weakly_connected.is_weakly_connected.html#networkx.algorithms.components.weakly_connected.is_weakly_connected">[docs]</a><span class="k">def</span> <span class="nf">is_weakly_connected</span><span class="p">(</span><span class="n">G</span><span class="p">):</span>
<span class="sd">"""Test directed graph for weak connectivity.</span>
<span class="sd"> Parameters</span>
<span class="sd"> ----------</span>
<span class="sd"> G : NetworkX Graph</span>
<span class="sd"> A directed graph.</span>
<span class="sd"> Returns</span>
<span class="sd"> -------</span>
<span class="sd"> connected : bool</span>
<span class="sd"> True if the graph is weakly connected, False otherwise.</span>
<span class="sd"> See Also</span>
<span class="sd"> --------</span>
<span class="sd"> strongly_connected_components</span>
<span class="sd"> Notes</span>
<span class="sd"> -----</span>
<span class="sd"> For directed graphs only. </span>
<span class="sd"> """</span>
<span class="k">if</span> <span class="ow">not</span> <span class="n">G</span><span class="o">.</span><span class="n">is_directed</span><span class="p">():</span>
<span class="k">raise</span> <span class="n">nx</span><span class="o">.</span><span class="n">NetworkXError</span><span class="p">(</span><span class="s">"""Not allowed for undirected graph G.</span>
<span class="s"> See is_connected() for connectivity test."""</span><span class="p">)</span>
<span class="k">if</span> <span class="nb">len</span><span class="p">(</span><span class="n">G</span><span class="p">)</span><span class="o">==</span><span class="mi">0</span><span class="p">:</span>
<span class="k">raise</span> <span class="n">nx</span><span class="o">.</span><span class="n">NetworkXPointlessConcept</span><span class="p">(</span>
<span class="sd">"""Connectivity is undefined for the null graph."""</span><span class="p">)</span>
<span class="k">return</span> <span class="nb">len</span><span class="p">(</span><span class="n">weakly_connected_components</span><span class="p">(</span><span class="n">G</span><span class="p">)[</span><span class="mi">0</span><span class="p">])</span><span class="o">==</span><span class="nb">len</span><span class="p">(</span><span class="n">G</span><span class="p">)</span>
</div>
<span class="k">def</span> <span class="nf">_single_source_shortest_unipath_length</span><span class="p">(</span><span class="n">G</span><span class="p">,</span><span class="n">source</span><span class="p">,</span><span class="n">cutoff</span><span class="o">=</span><span class="bp">None</span><span class="p">):</span>
<span class="sd">"""Compute the shortest path lengths from source to all reachable nodes.</span>
<span class="sd"> The direction of the edge between nodes is ignored.</span>
<span class="sd"> </span>
<span class="sd"> For directed graphs only.</span>
<span class="sd"> Parameters</span>
<span class="sd"> ----------</span>
<span class="sd"> G : NetworkX graph</span>
<span class="sd"> source : node</span>
<span class="sd"> Starting node for path</span>
<span class="sd"> cutoff : integer, optional</span>
<span class="sd"> Depth to stop the search. Only paths of length <= cutoff are returned.</span>
<span class="sd"> Returns</span>
<span class="sd"> -------</span>
<span class="sd"> lengths : dictionary</span>
<span class="sd"> Dictionary of shortest path lengths keyed by target.</span>
<span class="sd"> """</span>
<span class="c"># namespace speedups</span>
<span class="n">Gsucc</span> <span class="o">=</span> <span class="n">G</span><span class="o">.</span><span class="n">succ</span>
<span class="n">Gpred</span> <span class="o">=</span> <span class="n">G</span><span class="o">.</span><span class="n">pred</span>
<span class="n">seen</span><span class="o">=</span><span class="p">{}</span> <span class="c"># level (number of hops) when seen in BFS</span>
<span class="n">level</span><span class="o">=</span><span class="mi">0</span> <span class="c"># the current level</span>
<span class="n">nextlevel</span> <span class="o">=</span> <span class="nb">set</span><span class="p">([</span><span class="n">source</span><span class="p">])</span> <span class="c"># set of nodes to check at next level</span>
<span class="k">while</span> <span class="n">nextlevel</span><span class="p">:</span>
<span class="n">thislevel</span><span class="o">=</span><span class="n">nextlevel</span> <span class="c"># advance to next level</span>
<span class="n">nextlevel</span> <span class="o">=</span> <span class="nb">set</span><span class="p">()</span> <span class="c"># and start a new list (fringe)</span>
<span class="k">for</span> <span class="n">v</span> <span class="ow">in</span> <span class="n">thislevel</span><span class="p">:</span>
<span class="k">if</span> <span class="n">v</span> <span class="ow">not</span> <span class="ow">in</span> <span class="n">seen</span><span class="p">:</span>
<span class="n">seen</span><span class="p">[</span><span class="n">v</span><span class="p">]</span><span class="o">=</span><span class="n">level</span> <span class="c"># set the level of vertex v</span>
<span class="n">nextlevel</span><span class="o">.</span><span class="n">update</span><span class="p">(</span><span class="n">Gsucc</span><span class="p">[</span><span class="n">v</span><span class="p">])</span> <span class="c"># add successors of v</span>
<span class="n">nextlevel</span><span class="o">.</span><span class="n">update</span><span class="p">(</span><span class="n">Gpred</span><span class="p">[</span><span class="n">v</span><span class="p">])</span> <span class="c"># add predecessors of v</span>
<span class="k">if</span> <span class="p">(</span><span class="n">cutoff</span> <span class="ow">is</span> <span class="ow">not</span> <span class="bp">None</span> <span class="ow">and</span> <span class="n">cutoff</span> <span class="o"><=</span> <span class="n">level</span><span class="p">):</span> <span class="k">break</span>
<span class="n">level</span><span class="o">=</span><span class="n">level</span><span class="o">+</span><span class="mi">1</span>
<span class="k">return</span> <span class="n">seen</span> <span class="c"># return all path lengths as dictionary</span>
</pre></div>
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