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<h1>Source code for networkx.algorithms.components.connected</h1><div class="highlight"><pre>
<span class="c"># -*- coding: utf-8 -*-</span>
<span class="sd">"""</span>
<span class="sd">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">'Eben Kenah'</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_connected_components'</span><span class="p">,</span>
<span class="s">'connected_components'</span><span class="p">,</span>
<span class="s">'connected_component_subgraphs'</span><span class="p">,</span>
<span class="s">'is_connected'</span><span class="p">,</span>
<span class="s">'node_connected_component'</span><span class="p">,</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="connected_components"><a class="viewcode-back" href="../../../../reference/generated/networkx.algorithms.components.connected.connected_components.html#networkx.algorithms.components.connected.connected_components">[docs]</a><span class="k">def</span> <span class="nf">connected_components</span><span class="p">(</span><span class="n">G</span><span class="p">):</span>
<span class="sd">"""Return nodes in connected components of graph.</span>
<span class="sd"> Parameters</span>
<span class="sd"> ----------</span>
<span class="sd"> G : NetworkX Graph</span>
<span class="sd"> An undirected graph.</span>
<span class="sd"> Returns</span>
<span class="sd"> -------</span>
<span class="sd"> comp : list of lists</span>
<span class="sd"> A list of nodes for each component of G.</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"> The list is ordered from largest connected component to smallest.</span>
<span class="sd"> For undirected graphs only. </span>
<span class="sd"> """</span>
<span class="k">if</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 directed graph G.</span>
<span class="s"> Use UG=G.to_undirected() to create an undirected graph."""</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">nx</span><span class="o">.</span><span class="n">single_source_shortest_path_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_connected_components"><a class="viewcode-back" href="../../../../reference/generated/networkx.algorithms.components.connected.number_connected_components.html#networkx.algorithms.components.connected.number_connected_components">[docs]</a><span class="k">def</span> <span class="nf">number_connected_components</span><span class="p">(</span><span class="n">G</span><span class="p">):</span>
<span class="sd">"""Return number of connected components in graph.</span>
<span class="sd"> Parameters</span>
<span class="sd"> ----------</span>
<span class="sd"> G : NetworkX Graph</span>
<span class="sd"> An undirected graph.</span>
<span class="sd"> Returns</span>
<span class="sd"> -------</span>
<span class="sd"> n : integer</span>
<span class="sd"> Number of connected components</span>
<span class="sd"> See Also </span>
<span class="sd"> --------</span>
<span class="sd"> connected_components</span>
<span class="sd"> Notes</span>
<span class="sd"> -----</span>
<span class="sd"> For undirected graphs only. </span>
<span class="sd"> """</span>
<span class="k">return</span> <span class="nb">len</span><span class="p">(</span><span class="n">connected_components</span><span class="p">(</span><span class="n">G</span><span class="p">))</span>
</div>
<div class="viewcode-block" id="is_connected"><a class="viewcode-back" href="../../../../reference/generated/networkx.algorithms.components.connected.is_connected.html#networkx.algorithms.components.connected.is_connected">[docs]</a><span class="k">def</span> <span class="nf">is_connected</span><span class="p">(</span><span class="n">G</span><span class="p">):</span>
<span class="sd">"""Test graph connectivity.</span>
<span class="sd"> Parameters</span>
<span class="sd"> ----------</span>
<span class="sd"> G : NetworkX Graph</span>
<span class="sd"> An undirected 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 connected, false otherwise.</span>
<span class="sd"> Examples</span>
<span class="sd"> --------</span>
<span class="sd"> >>> G=nx.path_graph(4)</span>
<span class="sd"> >>> print(nx.is_connected(G))</span>
<span class="sd"> True</span>
<span class="sd"> See Also</span>
<span class="sd"> --------</span>
<span class="sd"> connected_components</span>
<span class="sd"> Notes</span>
<span class="sd"> -----</span>
<span class="sd"> For undirected graphs only. </span>
<span class="sd"> """</span>
<span class="k">if</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="sd">"""Not allowed for directed graph G.</span>
<span class="sd">Use UG=G.to_undirected() to create an undirected graph."""</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">nx</span><span class="o">.</span><span class="n">single_source_shortest_path_length</span><span class="p">(</span><span class="n">G</span><span class="p">,</span>
<span class="nb">next</span><span class="p">(</span><span class="n">G</span><span class="o">.</span><span class="n">nodes_iter</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>
<div class="viewcode-block" id="connected_component_subgraphs"><a class="viewcode-back" href="../../../../reference/generated/networkx.algorithms.components.connected.connected_component_subgraphs.html#networkx.algorithms.components.connected.connected_component_subgraphs">[docs]</a><span class="k">def</span> <span class="nf">connected_component_subgraphs</span><span class="p">(</span><span class="n">G</span><span class="p">):</span>
<span class="sd">"""Return connected components as subgraphs.</span>
<span class="sd"> Parameters</span>
<span class="sd"> ----------</span>
<span class="sd"> G : NetworkX Graph</span>
<span class="sd"> An undirected graph.</span>
<span class="sd"> Returns</span>
<span class="sd"> -------</span>
<span class="sd"> glist : list</span>
<span class="sd"> A list of graphs, one for each connected component of G.</span>
<span class="sd"> Examples</span>
<span class="sd"> --------</span>
<span class="sd"> Get largest connected component as subgraph</span>
<span class="sd"> >>> G=nx.path_graph(4)</span>
<span class="sd"> >>> G.add_edge(5,6)</span>
<span class="sd"> >>> H=nx.connected_component_subgraphs(G)[0]</span>
<span class="sd"> See Also</span>
<span class="sd"> --------</span>
<span class="sd"> connected_components</span>
<span class="sd"> Notes</span>
<span class="sd"> -----</span>
<span class="sd"> The list is ordered from largest connected component to smallest.</span>
<span class="sd"> For undirected graphs only. </span>
<span class="sd"> Graph, node, and edge attributes are copied to the subgraphs.</span>
<span class="sd"> """</span>
<span class="n">cc</span><span class="o">=</span><span class="n">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">cc</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="node_connected_component"><a class="viewcode-back" href="../../../../reference/generated/networkx.algorithms.components.connected.node_connected_component.html#networkx.algorithms.components.connected.node_connected_component">[docs]</a><span class="k">def</span> <span class="nf">node_connected_component</span><span class="p">(</span><span class="n">G</span><span class="p">,</span><span class="n">n</span><span class="p">):</span>
<span class="sd">"""Return nodes in connected components of graph containing node n.</span>
<span class="sd"> Parameters</span>
<span class="sd"> ----------</span>
<span class="sd"> G : NetworkX Graph</span>
<span class="sd"> An undirected graph.</span>
<span class="sd"> n : node label </span>
<span class="sd"> A node in G</span>
<span class="sd"> Returns</span>
<span class="sd"> -------</span>
<span class="sd"> comp : lists</span>
<span class="sd"> A list of nodes in component of G containing node n.</span>
<span class="sd"> See Also </span>
<span class="sd"> --------</span>
<span class="sd"> connected_components</span>
<span class="sd"> Notes</span>
<span class="sd"> -----</span>
<span class="sd"> For undirected graphs only. </span>
<span class="sd"> """</span>
<span class="k">if</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 directed graph G.</span>
<span class="s"> Use UG=G.to_undirected() to create an undirected graph."""</span><span class="p">)</span>
<span class="k">return</span> <span class="nb">list</span><span class="p">(</span><span class="n">nx</span><span class="o">.</span><span class="n">single_source_shortest_path_length</span><span class="p">(</span><span class="n">G</span><span class="p">,</span><span class="n">n</span><span class="p">)</span><span class="o">.</span><span class="n">keys</span><span class="p">())</span>
</div>
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