Source code for networkx.generators.triads

# See
# Copyright 2011 Reya Group <>
# Copyright 2011 Alex Levenson <>
# Copyright 2011 Diederik van Liere <>
"""Functions that generate the triad graphs, that is, the possible
digraphs on three nodes.

import networkx as nx
from networkx.classes import DiGraph

__all__ = ["triad_graph"]

#: Dictionary mapping triad name to list of directed edges in the
#: digraph representation of that triad (with nodes 'a', 'b', and 'c').
    "003": [],
    "012": ["ab"],
    "102": ["ab", "ba"],
    "021D": ["ba", "bc"],
    "021U": ["ab", "cb"],
    "021C": ["ab", "bc"],
    "111D": ["ac", "ca", "bc"],
    "111U": ["ac", "ca", "cb"],
    "030T": ["ab", "cb", "ac"],
    "030C": ["ba", "cb", "ac"],
    "201": ["ab", "ba", "ac", "ca"],
    "120D": ["bc", "ba", "ac", "ca"],
    "120U": ["ab", "cb", "ac", "ca"],
    "120C": ["ab", "bc", "ac", "ca"],
    "210": ["ab", "bc", "cb", "ac", "ca"],
    "300": ["ab", "ba", "bc", "cb", "ac", "ca"],

[docs] @nx._dispatch(graphs=None) def triad_graph(triad_name): """Returns the triad graph with the given name. Each string in the following tuple is a valid triad name:: ('003', '012', '102', '021D', '021U', '021C', '111D', '111U', '030T', '030C', '201', '120D', '120U', '120C', '210', '300') Each triad name corresponds to one of the possible valid digraph on three nodes. Parameters ---------- triad_name : string The name of a triad, as described above. Returns ------- :class:`~networkx.DiGraph` The digraph on three nodes with the given name. The nodes of the graph are the single-character strings 'a', 'b', and 'c'. Raises ------ ValueError If `triad_name` is not the name of a triad. See also -------- triadic_census """ if triad_name not in TRIAD_EDGES: raise ValueError( f'unknown triad name "{triad_name}"; use one of the triad names' " in the TRIAD_NAMES constant" ) G = DiGraph() G.add_nodes_from("abc") G.add_edges_from(TRIAD_EDGES[triad_name]) return G