def has_cycle(G):
"""Decides whether the directed graph has a cycle."""
try:
consume(topological_sort(G))
except nx.NetworkXUnfeasible:
return True
else:
return False
def has_cycle(G):
"""Decides whether the directed graph has a cycle."""
try:
consume(topological_sort(G))
except nx.NetworkXUnfeasible:
return True
else:
return False
def test_topological_sort2(self):
DG = nx.DiGraph({1: [2], 2: [3], 3: [4],
4: [5], 5: [1], 11: [12],
12: [13], 13: [14], 14: [15]})
pytest.raises(nx.NetworkXUnfeasible, consume, nx.topological_sort(DG))
assert not nx.is_directed_acyclic_graph(DG)
DG.remove_edge(1, 2)
consume(nx.topological_sort(DG))
assert nx.is_directed_acyclic_graph(DG)
def test_topological_sort2(self):
DG = nx.DiGraph({1: [2], 2: [3], 3: [4],
4: [5], 5: [1], 11: [12],
12: [13], 13: [14], 14: [15]})
assert_raises(nx.NetworkXUnfeasible, consume, nx.topological_sort(DG))
assert_false(nx.is_directed_acyclic_graph(DG))
DG.remove_edge(1, 2)
consume(nx.topological_sort(DG))
assert_true(nx.is_directed_acyclic_graph(DG))
def is_directed_acyclic_graph(G):
"""Return True if the graph `G` is a directed acyclic graph (DAG) or
False if not.
Parameters
----------
G : NetworkX graph
Returns
-------
bool
True if `G` is a DAG, False otherwise
"""
if not G.is_directed():
return False
try:
consume(topological_sort(G))
return True
except nx.NetworkXUnfeasible:
return False
def is_directed_acyclic_graph(G):
"""Return True if the graph `G` is a directed acyclic graph (DAG) or
False if not.
Parameters
----------
G : NetworkX graph
Returns
-------
bool
True if `G` is a DAG, False otherwise
"""
if not G.is_directed():
return False
try:
consume(topological_sort(G))
return True
except nx.NetworkXUnfeasible:
return False
