"""Unary operations on graphs"""
import networkx as nx
__all__ = ["complement", "reverse"]
def complement(G):
"""Returns the graph complement of G.
Parameters
----------
G : graph
A NetworkX graph
Returns
-------
GC : A new graph.
Notes
------
Note that complement() does not create self-loops and also
does not produce parallel edges for MultiGraphs.
Graph, node, and edge data are not propagated to the new graph.
"""
R = G.__class__()
R.add_nodes_from(G)
R.add_edges_from(
((n, n2) for n, nbrs in G.adjacency() for n2 in G if n2 not in nbrs if n != n2)
)
return R
def reverse(G, copy=True):
"""Returns the reverse directed graph of G.
Parameters
----------
G : directed graph
A NetworkX directed graph
copy : bool
If True, then a new graph is returned. If False, then the graph is
reversed in place.
Returns
-------
H : directed graph
The reversed G.
"""
if not G.is_directed():
raise nx.NetworkXError("Cannot reverse an undirected graph.")
else:
return G.reverse(copy=copy)