"""Helper functions for community-finding algorithms."""
__all__ = ["is_partition"]
[docs]def is_partition(G, communities):
"""Returns *True* if `communities` is a partition of the nodes of `G`.
A partition of a universe set is a family of pairwise disjoint sets
whose union is the entire universe set.
Parameters
----------
G : NetworkX graph.
communities : list or iterable of sets of nodes
If not a list, the iterable is converted internally to a list.
If it is an iterator it is exhausted.
"""
# Alternate implementation:
# return all(sum(1 if v in c else 0 for c in communities) == 1 for v in G)
if not isinstance(communities, list):
communities = list(communities)
nodes = {n for c in communities for n in c if n in G}
return len(G) == len(nodes) == sum(len(c) for c in communities)