empty_graph

empty_graph(n=0, create_using=None, default=<class 'networkx.classes.graph.Graph'>)

Returns the empty graph with n nodes and zero edges.

Parameters

nint or iterable container of nodes (default = 0)

If n is an integer, nodes are from range(n). If n is a container of nodes, those nodes appear in the graph.

create_usingGraph Instance, Constructor or None

Indicator of type of graph to return. If a Graph-type instance, then clear and use it. If None, use the default constructor. If a constructor, call it to create an empty graph.

defaultGraph constructor (optional, default = nx.Graph)

The constructor to use if create_using is None. If None, then nx.Graph is used. This is used when passing an unknown create_using value through your home-grown function to empty_graph and you want a default constructor other than nx.Graph.

Notes

The variable create_using should be a Graph Constructor or a “graph”-like object. Constructors, e.g. nx.Graph or nx.MultiGraph will be used to create the returned graph. “graph”-like objects will be cleared (nodes and edges will be removed) and refitted as an empty “graph” with nodes specified in n. This capability is useful for specifying the class-nature of the resulting empty “graph” (i.e. Graph, DiGraph, MyWeirdGraphClass, etc.).

The variable create_using has three main uses: Firstly, the variable create_using can be used to create an empty digraph, multigraph, etc. For example,

>>> n = 10
>>> G = nx.empty_graph(n, create_using=nx.DiGraph)

will create an empty digraph on n nodes.

Secondly, one can pass an existing graph (digraph, multigraph, etc.) via create_using. For example, if G is an existing graph (resp. digraph, multigraph, etc.), then empty_graph(n, create_using=G) will empty G (i.e. delete all nodes and edges using G.clear()) and then add n nodes and zero edges, and return the modified graph.

Thirdly, when constructing your home-grown graph creation function you can use empty_graph to construct the graph by passing a user defined create_using to empty_graph. In this case, if you want the default constructor to be other than nx.Graph, specify default.

>>> def mygraph(n, create_using=None):
...     G = nx.empty_graph(n, create_using, nx.MultiGraph)
...     G.add_edges_from([(0, 1), (0, 1)])
...     return G
>>> G = mygraph(3)
>>> G.is_multigraph()
True
>>> G = mygraph(3, nx.Graph)
>>> G.is_multigraph()
False

See also create_empty_copy(G).

Examples

>>> G = nx.empty_graph(10)
>>> G.number_of_nodes()
10
>>> G.number_of_edges()
0
>>> G = nx.empty_graph("ABC")
>>> G.number_of_nodes()
3
>>> sorted(G)
['A', 'B', 'C']