Module operators

Return the subgraph induced on nodes in nbunch.

nbunch: can be a singleton node, a string (which is treated as a singleton node), or any iterable container of of nodes. (It can be an iterable or an iterator, e.g. a list, set, graph, file, numeric array, etc.)

Setting inplace=True will return the induced subgraph in the original graph by deleting nodes not in nbunch. This overrides create_using. Warning: this can destroy the graph.

Unless otherwise specified, return a new graph of the same type as self. Use (optional) create_using=R to return the resulting subgraph in R. R can be an existing graph-like object (to be emptied) or R is a call to a graph object, e.g. create_using=DiGraph(). See documentation for empty_graph.

Implemented for Graph, DiGraph, XGraph, XDiGraph

Note: subgraph(G) calls G.subgraph()

Return the union of graphs G and H.

Graphs G and H must be disjoint, otherwise an exception is raised.

Node names of G and H can be changed be specifying the tuple rename=('G-','H-') (for example). Node u in G is then renamed "G-u" and v in H is renamed "H-v".

To force a disjoint union with node relabeling, use disjoint_union(G,H) or convert_node_labels_to integers().

Optional create_using=R returns graph R filled in with the union of G and H. Otherwise a new graph is created, of the same class as G. It is recommended that G and H be either both directed or both undirected.

A new name can be specified in the form X=graph_union(G,H,name="new_name")

Implemented for Graph, DiGraph, XGraph, XDiGraph.

Return the disjoint union of graphs G and H, forcing distinct integer node labels.

A new graph is created, of the same class as G. It is recommended that G and H be either both directed or both undirected.

Implemented for Graph, DiGraph, XGraph, XDiGraph.

Return the Cartesian product of G and H.

Tested only on Graph class.

Return a new graph of G composed with H.

The node sets of G and H need not be disjoint.

A new graph is returned, of the same class as G. It is recommended that G and H be either both directed or both undirected.

Optional create_using=R returns graph R filled in with the compose(G,H). Otherwise a new graph is created, of the same class as G. It is recommended that G and H be either both directed or both undirected.

Implemented for Graph, DiGraph, XGraph, XDiGraph

Return graph complement of G.

Unless otherwise specified, return a new graph of the same type as self. Use (optional) create_using=R to return the resulting subgraph in R. R can be an existing graph-like object (to be emptied) or R can be a call to a graph object, e.g. create_using=DiGraph(). See documentation for empty_graph()

Implemented for Graph, DiGraph, XGraph, XDiGraph. Note that complement() is not well-defined for XGraph and XDiGraph objects that allow multiple edges or self-loops.

Return a new undirected representation of the graph G.

Works for Graph, DiGraph, XGraph, XDiGraph.

Note: convert_to_undirected(G)=G.to_undirected()

Return a new directed representation of the graph G.

Works for Graph, DiGraph, XGraph, XDiGraph.

Note: convert_to_directed(G)=G.to_directed()

Return a copy of G with node labels transformed by mapping.

mapping is either

• a dictionary with the old labels as keys and new labels as values
• a function transforming an old label with a new label

In either case, the new labels must be hashable Python objects.

mapping as dictionary:

>>> G=path_graph(3)  # nodes 0-1-2
>>> mapping={0:'a',1:'b',2:'c'}
>>> H=relabel_nodes(G,mapping)
>>> print H.nodes()
['a', 'c', 'b']

>>> G=path_graph(26) # nodes 0..25
>>> mapping=dict(zip(G.nodes(),"abcdefghijklmnopqrstuvwxyz"))
>>> H=relabel_nodes(G,mapping) # nodes a..z
>>> mapping=dict(zip(G.nodes(),xrange(1,27)))
>>> G1=relabel_nodes(G,mapping) # nodes 1..26

mapping as function

>>> G=path_graph(3)
>>> def mapping(x):
...    return x**2
>>> H=relabel_nodes(G,mapping)
>>> print H.nodes()
[0, 1, 4]

Also see convert_node_labels_to_integers.

Return a copy of G, with n node labels replaced with integers, starting at first_label.

first_label: (optional, default=0)

An integer specifying the offset in numbering nodes. The n new integer labels are numbered first_label, ..., n+first_label.

ordering: (optional, default="default")

A string specifying how new node labels are ordered. Possible values are:

"default" : inherit node ordering from G.nodes() "sorted" : inherit node ordering from sorted(G.nodes()) "increasing degree" : nodes are sorted by increasing degree "decreasing degree" : nodes are sorted by decreasing degree

discard_old_labels

if True (default) discard old labels if False, create a dict self.node_labels that maps new labels to old labels

Works for Graph, DiGraph, XGraph, XDiGraph