def test_undirected_graph_remove_vertex(self):
""" Remove vertices from an undirected graph """
g = UndirectedGraph()
g.add_vertex(v_val='v0')
g.add_vertex(v_val='v1')
g.add_vertex(v_val='v2')
g.add_edge(('v0', 'v1'))
g.add_edge(('v1', 'v2'))
g.remove_vertex('v0')
self.assertFalse(g.has_vertex('v0'))
self.assertTrue(g.has_vertex('v1'))
self.assertTrue(g.has_vertex('v2'))
self.assertFalse(g.has_edge(('v0', 'v1')))
self.assertFalse(g.has_edge(('v1', 'v0')))
self.assertTrue(g.has_edge(('v1', 'v2')))
g.remove_vertex('v1')
self.assertFalse(g.has_vertex('v0'))
self.assertFalse(g.has_vertex('v1'))
self.assertTrue(g.has_vertex('v2'))
self.assertFalse(g.has_edge(('v0', 'v1')))
self.assertFalse(g.has_edge(('v1', 'v0')))
self.assertFalse(g.has_edge(('v1', 'v2')))
def test_undirected_graph_vertex_already_exists(self):
""" An undirected graph should not be able to add a vertex that already
exists in the graph """
g = UndirectedGraph()
g.add_vertex(v_val='v0')
with self.assertRaises(ValueError):
g.add_vertex(v_val='v0')
def test_undirected_graph_edge_already_exists_exception(self):
""" An undirected graph should not be able to add an edge that already
exists in the graph """
g = UndirectedGraph()
g.add_vertex(v_val='v0')
g.add_vertex(v_val='v1')
g.add_edge(('v0', 'v1'))
with self.assertRaises(ValueError):
g.add_edge(('v1', 'v0'))
def test_undirected_graph_add_vertex(self):
""" Add vertices to an undirected graph """
g = UndirectedGraph()
v0_val = g.add_vertex(v_val='v0', attrs={'city': 'Modena'})
v1_val = g.add_vertex(v_val='v1')
self.assertEqual(v0_val, 'v0')
self.assertEqual(v1_val, 'v1')
self.assertTrue(g.has_vertex('v0'))
self.assertTrue(g.has_vertex('v1'))
self.assertFalse(g.has_vertex('v2'))
self.assertEqual(g.get_vertex(v0_val).get('city'), 'Modena')
self.assertIsNone(g.get_vertex(v1_val).get('city'))
def test_undirected_graph_add_edge(self):
""" Add edges to an undirected graph """
g = UndirectedGraph()
g.add_vertex(v_val='v0')
g.add_vertex(v_val='v1')
g.add_edge(('v0', 'v0'), attrs={'weight': 5})
g.add_edge(('v0', 'v1'), attrs={'weight': 7})
e00 = g.get_edge(('v0', 'v0'))
e01 = g.get_edge(('v0', 'v1'))
self.assertTrue(g.has_edge(('v0', 'v0')))
self.assertTrue(g.has_edge(('v0', 'v1')))
self.assertFalse(g.has_edge(('v0', 'v2')))
self.assertTrue(g.has_edge(('v1', 'v0')))
self.assertEqual(e00.get('weight'), 5)
self.assertEqual(e01.get('weight'), 7)
def test_undirected_graph_vertices_and_edges(self):
""" Get undirected graphs' vertices and edges properties """
g = UndirectedGraph()
g.add_vertex(v_val='v0')
g.add_vertex(v_val='v1')
g.add_edge(('v0', 'v1'))
v0 = g.get_vertex('v0')
v1 = g.get_vertex('v1')
e01 = g.get_edge(('v0', 'v1'))
self.assertEqual(set(g.vertices), set([v0, v1]))
self.assertEqual(set(g.edges), set([e01]))
with self.assertRaises(AttributeError):
g.vertices = set()
with self.assertRaises(AttributeError):
g.edges = set()
def test_undirected_graph_iteration(self):
""" Iterate through an undirected graph """
g = UndirectedGraph()
counter = 0
for v in g:
counter += 1
self.assertEqual(counter, 0)
g.add_vertex(v_val='v0')
g.add_vertex(v_val='v1')
g.add_edge(('v0', 'v1'))
for v in g:
counter += 1
self.assertTrue(g.has_vertex(v.val))
self.assertEqual(counter, 2)
def test_undirected_graph_length(self):
""" Get the length of an undirected graph """
g = UndirectedGraph()
self.assertEqual(len(g), 0)
g.add_vertex(v_val='v0')
self.assertEqual(len(g), 1)
g.add_vertex(v_val='v1')
g.add_edge(('v0', 'v1'))
self.assertEqual(len(g), 2)
g.remove_vertex('v0')
self.assertEqual(len(g), 1)
def test_undirected_graph_dijkstra(self):
""" Perform Dijkstra's algorithm on an undirected graph """
""" 1_ E 1_ E
| / | /
A- 1 -B- 5 -D A- 3 -B- 5 -D
\ | \ |
2 0 2 -2
\ | \ |
C C
"""
g = UndirectedGraph()
g.add_vertex(v_val='A')
g.add_vertex(v_val='B')
g.add_vertex(v_val='C')
g.add_vertex(v_val='D')
g.add_vertex(v_val='E')
g.add_edge(('A', 'A'), attrs={'weight': 1})
g.add_edge(('A', 'B'), attrs={'weight': 1})
g.add_edge(('A', 'C'), attrs={'weight': 2})
g.add_edge(('B', 'C'), attrs={'weight': 0})
g.add_edge(('B', 'D'), attrs={'weight': 5})
negative_weight_g = g.clone()
negative_weight_g.get_edge(('A', 'B')).set('weight', 3)
negative_weight_g.get_edge(('B', 'C')).set('weight', -2)
missing_weight_g = g.clone()
missing_weight_g.get_edge(('A', 'B')).set('weight', None)
self.assertEqual(g.dijkstra('A', goal_val='A'), ['A'])
self.assertEqual(g.dijkstra('A', goal_val='B'), ['A', 'B'])
self.assertEqual(g.dijkstra('A', goal_val='C'), ['A', 'B', 'C'])
self.assertEqual(g.dijkstra('A', goal_val='D'), ['A', 'B', 'D'])
self.assertIsNone(g.dijkstra('A', goal_val='E'))
# when returning all paths (no goal specified), paths aren't evaluated
# until requested, to avoid the O(|V|^2) cost of backtracking |V| paths
A_paths = g.dijkstra('A')
# request each key
_ = [A_paths[v.val] for v in g]
self.assertEqual(dict(A_paths), {'A': ['A'],
'B': ['A', 'B'],
'C': ['A', 'B', 'C'],
'D': ['A', 'B', 'D'],
'E': None})
self.assertEqual(g.dijkstra('A', goal_val='A', return_distances=True),
0)
self.assertEqual(g.dijkstra('A', goal_val='B', return_distances=True),
1)
self.assertEqual(g.dijkstra('A', goal_val='C', return_distances=True),
1)
self.assertEqual(g.dijkstra('A', goal_val='D', return_distances=True),
6)
self.assertEqual(g.dijkstra('A', goal_val='E', return_distances=True),
float('inf'))
self.assertEqual(g.dijkstra('A', return_distances=True),
{'A': 0, 'B': 1, 'C': 1, 'D': 6, 'E': float('inf')})
with self.assertRaises(ValueError):
negative_weight_g.dijkstra('A')
with self.assertRaises(ValueError):
missing_weight_g.dijkstra('A')
def test_undirected_graph_search(self):
""" Search for paths from an undirected vertex to all vertices reachable
from it """
""" __
| /
v0 - v1 - v3
\
v2
"""
g = UndirectedGraph()
g.add_vertex(v_val='v0')
g.add_vertex(v_val='v1')
g.add_vertex(v_val='v2')
g.add_vertex(v_val='v3')
g.add_vertex(v_val='v4')
g.add_edge(('v0', 'v0'))
g.add_edge(('v0', 'v1'))
g.add_edge(('v0', 'v2'))
g.add_edge(('v1', 'v3'))
self.assertEqual(g.search('v0', goal_val='v0'), ['v0'])
self.assertEqual(g.search('v0', goal_val='v1'), ['v0', 'v1'])
self.assertEqual(g.search('v0', goal_val='v2'), ['v0', 'v2'])
self.assertEqual(g.search('v0', goal_val='v3'), ['v0', 'v1', 'v3'])
self.assertIsNone(g.search('v0', goal_val='v4'))
self.assertEqual(g.search('v0'), {'v0': ['v0'],
'v1': ['v0', 'v1'],
'v2': ['v0', 'v2'],
'v3': ['v0', 'v1', 'v3']})
self.assertEqual(g.search('v0', goal_val='v0', method='depth_first'),
['v0'])
self.assertEqual(g.search('v0', goal_val='v1', method='depth_first'),
['v0', 'v1'])
self.assertEqual(g.search('v0', goal_val='v2', method='depth_first'),
['v0', 'v2'])
self.assertEqual(g.search('v0', goal_val='v3', method='depth_first'),
['v0', 'v1', 'v3'])
self.assertIsNone(g.search('v0', goal_val='v4', method='depth_first'))
self.assertEqual(g.search('v0', method='depth_first'),
{'v0': ['v0'],
'v1': ['v0', 'v1'],
'v2': ['v0', 'v2'],
'v3': ['v0', 'v1', 'v3']})
