Source code for networkx.algorithms.operators.all

"""Operations on many graphs.
"""
from itertools import zip_longest
import networkx as nx

__all__ = ["union_all", "compose_all", "disjoint_union_all", "intersection_all"]


[docs]def union_all(graphs, rename=(None,)): """Returns the union of all graphs. The graphs must be disjoint, otherwise an exception is raised. Parameters ---------- graphs : list of graphs List of NetworkX graphs rename : bool , default=(None, None) Node names of G and H can be changed by 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". Returns ------- U : a graph with the same type as the first graph in list Raises ------ ValueError If `graphs` is an empty list. Notes ----- To force a disjoint union with node relabeling, use disjoint_union_all(G,H) or convert_node_labels_to integers(). Graph, edge, and node attributes are propagated to the union graph. If a graph attribute is present in multiple graphs, then the value from the last graph in the list with that attribute is used. See Also -------- union disjoint_union_all """ if not graphs: raise ValueError("cannot apply union_all to an empty list") graphs_names = zip_longest(graphs, rename) U, gname = next(graphs_names) for H, hname in graphs_names: U = nx.union(U, H, (gname, hname)) gname = None return U
[docs]def disjoint_union_all(graphs): """Returns the disjoint union of all graphs. This operation forces distinct integer node labels starting with 0 for the first graph in the list and numbering consecutively. Parameters ---------- graphs : list List of NetworkX graphs Returns ------- U : A graph with the same type as the first graph in list Raises ------ ValueError If `graphs` is an empty list. Notes ----- It is recommended that the graphs be either all directed or all undirected. Graph, edge, and node attributes are propagated to the union graph. If a graph attribute is present in multiple graphs, then the value from the last graph in the list with that attribute is used. """ if not graphs: raise ValueError("cannot apply disjoint_union_all to an empty list") graphs = iter(graphs) U = next(graphs) for H in graphs: U = nx.disjoint_union(U, H) return U
[docs]def compose_all(graphs): """Returns the composition of all graphs. Composition is the simple union of the node sets and edge sets. The node sets of the supplied graphs need not be disjoint. Parameters ---------- graphs : list List of NetworkX graphs Returns ------- C : A graph with the same type as the first graph in list Raises ------ ValueError If `graphs` is an empty list. Notes ----- It is recommended that the supplied graphs be either all directed or all undirected. Graph, edge, and node attributes are propagated to the union graph. If a graph attribute is present in multiple graphs, then the value from the last graph in the list with that attribute is used. """ if not graphs: raise ValueError("cannot apply compose_all to an empty list") graphs = iter(graphs) C = next(graphs) for H in graphs: C = nx.compose(C, H) return C
[docs]def intersection_all(graphs): """Returns a new graph that contains only the nodes and the edges that exist in all graphs. Parameters ---------- graphs : list List of NetworkX graphs Returns ------- R : A new graph with the same type as the first graph in list Raises ------ ValueError If `graphs` is an empty list. Notes ----- Attributes from the graph, nodes, and edges are not copied to the new graph. """ if not graphs: raise ValueError("cannot apply intersection_all to an empty list") graphs = iter(graphs) R = next(graphs) for H in graphs: R = nx.intersection(R, H) return R