### view env/lib/python3.9/site-packages/networkx/algorithms/components/semiconnected.py @ 0:4f3585e2f14bdraftdefaulttip

author shellac Mon, 22 Mar 2021 18:12:50 +0000
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```
"""Semiconnectedness."""
import networkx as nx
from networkx.utils import not_implemented_for, pairwise

__all__ = ["is_semiconnected"]

@not_implemented_for("undirected")
def is_semiconnected(G, topo_order=None):
"""Returns True if the graph is semiconnected, False otherwise.

A graph is semiconnected if, and only if, for any pair of nodes, either one
is reachable from the other, or they are mutually reachable.

Parameters
----------
G : NetworkX graph
A directed graph.

topo_order: list or tuple, optional
A topological order for G (if None, the function will compute one)

Returns
-------
semiconnected : bool
True if the graph is semiconnected, False otherwise.

Raises
------
NetworkXNotImplemented
If the input graph is undirected.

NetworkXPointlessConcept
If the graph is empty.

Examples
--------
>>> G = nx.path_graph(4, create_using=nx.DiGraph())
>>> print(nx.is_semiconnected(G))
True
>>> G = nx.DiGraph([(1, 2), (3, 2)])
>>> print(nx.is_semiconnected(G))
False

--------
is_strongly_connected
is_weakly_connected
is_connected
is_biconnected
"""
if len(G) == 0:
raise nx.NetworkXPointlessConcept(
"Connectivity is undefined for the null graph."
)

if not nx.is_weakly_connected(G):
return False

G = nx.condensation(G)
if topo_order is None:
topo_order = nx.topological_sort(G)

return all(G.has_edge(u, v) for u, v in pairwise(topo_order))
```