condensation#
- condensation(G, scc=None)[source]#
Returns the condensation of G.
The condensation of G is the graph with each of the strongly connected components contracted into a single node.
- Parameters:
- GNetworkX DiGraph
A directed graph.
- scc: list or generator (optional, default=None)
Strongly connected components. If provided, the elements in
scc
must partition the nodes inG
. If not provided, it will be calculated as scc=nx.strongly_connected_components(G).
- Returns:
- CNetworkX DiGraph
The condensation graph C of G. The node labels are integers corresponding to the index of the component in the list of strongly connected components of G. C has a graph attribute named ‘mapping’ with a dictionary mapping the original nodes to the nodes in C to which they belong. Each node in C also has a node attribute ‘members’ with the set of original nodes in G that form the SCC that the node in C represents.
- Raises:
- NetworkXNotImplemented
If G is undirected.
Notes
After contracting all strongly connected components to a single node, the resulting graph is a directed acyclic graph.
Examples
Contracting two sets of strongly connected nodes into two distinct SCC using the barbell graph.
>>> G = nx.barbell_graph(4, 0) >>> G.remove_edge(3, 4) >>> G = nx.DiGraph(G) >>> H = nx.condensation(G) >>> H.nodes.data() NodeDataView({0: {'members': {0, 1, 2, 3}}, 1: {'members': {4, 5, 6, 7}}}) >>> H.graph['mapping'] {0: 0, 1: 0, 2: 0, 3: 0, 4: 1, 5: 1, 6: 1, 7: 1}
Contracting a complete graph into one single SCC.
>>> G = nx.complete_graph(7, create_using=nx.DiGraph) >>> H = nx.condensation(G) >>> H.nodes NodeView((0,)) >>> H.nodes.data() NodeDataView({0: {'members': {0, 1, 2, 3, 4, 5, 6}}})