示例#1
0
class TestGraphAddEdgeExceptionWarning(UnittestPythonCompatibility):
    """
    Test logged warnings and raised Exceptions by Graph add_edge.
    Same as for add_nodes
    """

    def setUp(self):
        """
        Build empty graph to add a node to and test default state
        """

        self.graph = Graph()

    def test_add_edge_node_not_exist(self):
        """
        Test adding edges for nodes that do not exist
        """

        self.assertRaises(GraphitException, self.graph.add_edge, 1, 2)

    def test_add_edge_exist(self):
        """
        Test adding edges that already exist. A warning is logged
        but edge ID is returned
        """

        self.graph.add_nodes([1, 2])
        self.graph.add_edge(1, 2)

        eid = self.graph.add_edge(1, 2)
        self.assertTrue(eid, (1, 2))

    def test_remove_edge_exist(self):
        """
        Test removal of edges that do not exist should only log a warning
        """

        self.graph.add_nodes([1, 2])
        try:
            self.graph.remove_edge(1, 2)
        except GraphitException:
            self.fail('remove_edge raised GraphitException unexpectedly')
示例#2
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class TestGraphAddEdgeAttributes(UnittestPythonCompatibility):
    """
    Test additional attribute storage for Graph add_edge
    """

    def setUp(self):
        """
        Build Graph with a few nodes but no edges yet
        """

        self.graph = Graph()
        self.graph.add_nodes('graph')

        # Only nodes no edges yet
        self.assertTrue(len(self.graph) == 5)
        self.assertTrue(len(self.graph.nodes) == 5)
        self.assertTrue(len(self.graph.edges) == 0)
        self.assertTrue(len(self.graph.adjacency) == 5)
        self.assertTrue(all([len(a) == 0 for a in self.graph.adjacency.values()]))

        # auto_nid
        self.assertTrue(self.graph.data.auto_nid)

    def tearDown(self):
        """
        Test state after edge attribute addition
        """

        # If undirected, add reversed edges
        if not self.graph.directed:
            for edge, attr in list(self.edges.items()):
                self.edges[edge[::-1]] = attr

        for edge, attr in self.edges.items():

            self.assertTrue(edge in self.graph.edges)
            self.assertDictEqual(self.graph.edges[edge], attr)

    def test_add_edge_no_attribute(self):
        """
        No attributes added should yield empty dict
        """

        self.edges = {(1, 2): {}}

        for edge, attr in self.edges.items():
            self.graph.add_edge(*edge, **attr)

    def test_add_edge_single_attribute_undirected(self):
        """
        Add a single attribute
        :return:
        """

        self.edges = {(1, 2): {'weight': 2.33}}

        for edge, attr in self.edges.items():
            self.graph.add_edge(*edge, **attr)

    def test_add_edge_multiple_attributes_undirected(self):
        """
        Add a single attribute
        """

        self.edges = {(1, 2): {'test': True, 'pv': 1.44}}

        for edge, attr in self.edges.items():
            self.graph.add_edge(*edge, **attr)

    def test_add_edge_nested_attribute_undirected(self):
        """
        Test adding nested attributed, e.a. dict in dict
        """

        self.edges = {(1, 2): {'func': len, 'nested': {'weight': 1.22, 'leaf': True}}}

        for edge, attr in self.edges.items():
            self.graph.add_edge(*edge, **attr)

    def test_add_edge_single_attribute_directed(self):
        """
        Add a single attribute, directed
        :return:
        """

        self.graph.directed = True
        self.edges = {(1, 2): {'weight': 2.33}}

        for edge, attr in self.edges.items():
            self.graph.add_edge(*edge, **attr)

    def test_add_edge_multiple_attributes_directed(self):
        """
        Add a single attribute, directed
        """

        self.graph.directed = True
        self.edges = {(1, 2): {'test': True, 'pv': 1.44}}

        for edge, attr in self.edges.items():
            self.graph.add_edge(*edge, **attr)

    def test_add_edge_nested_attribute_directed(self):
        """
        Test adding nested attributed, e.a. dict in dict, directed
        """

        self.graph.directed = True
        self.edges = {(1, 2): {'func': len, 'nested': {'weight': 1.22, 'leaf': True}}}

        for edge, attr in self.edges.items():
            self.graph.add_edge(*edge, **attr)

    def test_add_edge_single_attribute_mixed(self):
        """
        Add a single attribute, override undirected graph
        """

        self.edges = {(1, 2): {'weight': 2.33}}

        for edge, attr in self.edges.items():
            self.graph.add_edge(*edge, directed=True, **attr)

        self.graph.directed = True
示例#3
0
class TestGraphAddEdge(UnittestPythonCompatibility):
    """
    Test Graph add_edge method with the Graph.auto_nid set to False
    mimicking the behaviour of many popular graph packages
    """

    def setUp(self):
        """
        Build Graph with a few nodes but no edges yet
        """

        self.graph = Graph(auto_nid=False)
        self.graph.add_nodes('graph')

        # Only nodes no edges yet
        self.assertTrue(len(self.graph) == 5)
        self.assertTrue(len(self.graph.nodes) == 5)
        self.assertTrue(len(self.graph.edges) == 0)
        self.assertTrue(len(self.graph.adjacency) == 5)
        self.assertTrue(all([len(a) == 0 for a in self.graph.adjacency.values()]))

        # auto_nid
        self.assertFalse(self.graph.data.auto_nid)

    def tearDown(self):
        """
        Test state after edge addition
        """

        # If undirected, add reversed edges
        if not self.graph.directed:
            self.edges.extend([e[::-1] for e in self.edges if e[::-1] not in self.edges])

        for edge in self.edges:

            # Edge should be present
            self.assertTrue(edge in self.graph.edges)

            # Nodes connected should be present
            self.assertTrue(all([node in self.graph.nodes for node in edge]))

            # Adjacency setup
            self.assertTrue(edge[1] in self.graph.adjacency[edge[0]])

            # If directional, reverse edge not in graph
            if self.graph.directed:
                rev_edge = edge[::-1]
                if rev_edge not in self.edges:
                    self.assertTrue(rev_edge not in self.graph.edges)

        # filled after addition
        self.assertTrue(len(self.graph) == 5)
        self.assertTrue(len(self.graph.nodes) == 5)
        self.assertTrue(len(self.graph.edges) == len(self.edges))
        self.assertTrue(len(self.graph.adjacency) == 5)

    def test_add_edge_undirectional(self):
        """
        Test adding a single un-directional edge
        """

        self.edges = [('g', 'r')]
        self.graph.add_edge(*self.edges[0])

    def test_add_edges_undirectional(self):
        """
        Test adding multiple un-directional edges
        """

        self.edges = [('g', 'r'), ('r', 'a'), ('a', 'p'), ('a', 'h'), ('p', 'h')]
        self.graph.add_edges(self.edges)

    def test_add_edge_directional(self):
        """
        Test adding a single directional edge
        """

        self.edges = [('g', 'r')]
        self.graph.directed = False
        self.graph.add_edge(*self.edges[0])

    def test_add_edges_directional(self):
        """
        Test adding multiple directional edges
        """

        self.edges = [('g', 'r'), ('r', 'a'), ('a', 'p'), ('a', 'h'), ('p', 'h')]
        self.graph.directed = False
        self.graph.add_edges(self.edges)

    def test_add_nodes_and_edges(self):
        """
        Test adding edges and creating the nodes from the edges.
        Auto_nid is set to False automatically to force identical
        node/edge names. When node exists, no message.
        """

        self.graph = Graph()

        self.edges = [('g', 'r'), ('r', 'a'), ('a', 'p'), ('a', 'h'), ('p', 'h')]
        self.graph.add_edges(self.edges, node_from_edge=True)
示例#4
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class TestGraphEdgeDirectionality(UnittestPythonCompatibility):
    """
    Test adding edges in directional or un-directional way
    """

    def setUp(self):
        """
        Build Graph with a few nodes but no edges yet
        """

        self.graph = Graph()
        self.graph.add_nodes([1, 2, 3])

        # Only nodes no edges yet
        self.assertTrue(len(self.graph) == 3)
        self.assertTrue(len(self.graph.nodes) == 3)
        self.assertTrue(len(self.graph.edges) == 0)
        self.assertTrue(len(self.graph.adjacency) == 3)
        self.assertTrue(all([len(a) == 0 for a in self.graph.adjacency.values()]))

    def tearDown(self):
        """
        Test state after edge addition
        """

        # If undirected, add reversed edges
        if not self.graph.directed:
            self.edges.extend([e[::-1] for e in self.edges if e[::-1] not in self.edges])

        for edge in self.edges:

            # Edge should be present
            self.assertTrue(edge in self.graph.edges)

            # Nodes connected should be present
            self.assertTrue(all([node in self.graph.nodes for node in edge]))

            # Adjacency setup
            self.assertTrue(edge[1] in self.graph.adjacency[edge[0]])

            # If directional, reverse edge not in graph
            if self.graph.directed:
                rev_edge = edge[::-1]
                if rev_edge not in self.edges:
                    self.assertTrue(rev_edge not in self.graph.edges)

        # filled after addition
        self.assertTrue(len(self.graph) == 3)
        self.assertTrue(len(self.graph.nodes) == 3)
        self.assertTrue(len(self.graph.edges) == len(self.edges))
        self.assertTrue(len(self.graph.adjacency) == 3)

    def test_add_edge_undirectional_graph(self):
        """
        Test default add edge in undirected graph
        """

        self.graph.directed = False
        self.edges = [(1, 2), (2, 3)]

        self.graph.add_edges(self.edges)

    def test_add_edge_directional_graph(self):
        """
        Test default add edge in directed graph
        """

        self.graph.directed = True
        self.edges = [(1, 2), (2, 3)]

        self.graph.add_edges(self.edges)

    def test_add_edge_mixed_graph(self):
        """
        Add edges with local override in directionality yielding a mixed
        directional graph
        """

        self.edges = [(1, 2), (2, 3), (3, 2)]

        self.graph.add_edge(1, 2, directed=True)
        self.graph.add_edge(2, 3)

        self.graph.directed = True
示例#5
0
class TestGraphAlgorithms(UnittestPythonCompatibility):
    def setUp(self):

        edges = {
            (1, 2): {
                'weight': 1.0
            },
            (2, 3): {
                'weight': 1.0
            },
            (2, 4): {
                'weight': 1.0
            },
            (3, 5): {
                'weight': 1.0
            },
            (4, 5): {
                'weight': 1.0
            },
            (4, 7): {
                'weight': 1.0
            },
            (5, 7): {
                'weight': 0.75
            },
            (3, 14): {
                'weight': 2.0
            },
            (14, 15): {
                'weight': 2.0
            },
            (14, 16): {
                'weight': 1.0
            },
            (15, 12): {
                'weight': 2.0
            },
            (22, 24): {
                'weight': 1.0
            },
            (12, 13): {
                'weight': 2.0
            },
            (13, 28): {
                'weight': 1.0
            },
            (5, 8): {
                'weight': 1.0
            },
            (8, 9): {
                'weight': 0.5
            },
            (8, 10): {
                'weight': 3.0
            },
            (9, 12): {
                'weight': 0.5
            },
            (10, 11): {
                'weight': 3.0
            },
            (11, 13): {
                'weight': 1.0
            },
            (7, 25): {
                'weight': 1.0
            },
            (25, 26): {
                'weight': 1.0
            },
            (26, 27): {
                'weight': 1.0
            },
            (11, 26): {
                'weight': 1.0
            },
            (7, 17): {
                'weight': 1.0
            },
            (17, 18): {
                'weight': 1.0
            },
            (18, 19): {
                'weight': 2.0
            },
            (18, 20): {
                'weight': 1.0
            },
            (20, 21): {
                'weight': 1.0
            },
            (21, 22): {
                'weight': 1.0
            },
            (22, 23): {
                'weight': 1.0
            }
        }

        # Regular graphit Graph
        self.graph = Graph(auto_nid=False)
        self.graph.directed = True

        # NetworkX graphit Graph
        self.gn = NetworkXGraph(auto_nid=False)
        self.gn.directed = True

        # NetworkX graph
        #self.nx = networkx.DiGraph()

        for eid in edges:
            self.graph.add_edge(node_from_edge=True, *eid, **edges[eid])
            self.gn.add_edge(node_from_edge=True, *eid, **edges[eid])
            #self.nx.add_edge(*eid, **edges[eid])

    def test_algorithm_degree(self):
        """
        Test degree method part of the Adjacency view
        """

        # Degree
        self.assertDictEqual(
            self.graph.adjacency.degree(), {
                1: 1,
                2: 3,
                3: 3,
                4: 3,
                5: 4,
                7: 4,
                14: 3,
                15: 2,
                16: 1,
                12: 3,
                22: 3,
                24: 1,
                13: 3,
                28: 1,
                8: 3,
                9: 2,
                10: 2,
                11: 3,
                25: 2,
                26: 3,
                27: 1,
                17: 2,
                18: 3,
                19: 1,
                20: 2,
                21: 2,
                23: 1
            })

        # Outdegree
        self.assertDictEqual(
            self.graph.adjacency.degree(method='outdegree'), {
                1: 1,
                2: 2,
                3: 2,
                4: 2,
                5: 2,
                7: 2,
                14: 2,
                15: 1,
                16: 0,
                12: 1,
                22: 2,
                24: 0,
                13: 1,
                28: 0,
                8: 2,
                9: 1,
                10: 1,
                11: 2,
                25: 1,
                26: 1,
                27: 0,
                17: 1,
                18: 2,
                19: 0,
                20: 1,
                21: 1,
                23: 0
            })

        # Indegree
        self.assertDictEqual(
            self.graph.adjacency.degree(method='indegree'), {
                1: 0,
                2: 1,
                3: 1,
                4: 1,
                5: 2,
                7: 2,
                14: 1,
                15: 1,
                16: 1,
                12: 2,
                22: 1,
                24: 1,
                13: 2,
                28: 1,
                8: 1,
                9: 1,
                10: 1,
                11: 1,
                25: 1,
                26: 2,
                27: 1,
                17: 1,
                18: 1,
                19: 1,
                20: 1,
                21: 1,
                23: 1
            })

        # Weighted degree
        self.assertDictEqual(
            self.graph.adjacency.degree(weight='weight'), {
                1: 1.0,
                2: 3.0,
                3: 4.0,
                4: 3.0,
                5: 3.75,
                7: 3.75,
                14: 5.0,
                15: 4.0,
                16: 1.0,
                12: 4.5,
                22: 3.0,
                24: 1.0,
                13: 4.0,
                28: 1.0,
                8: 4.5,
                9: 1.0,
                10: 6.0,
                11: 5.0,
                25: 2.0,
                26: 3.0,
                27: 1.0,
                17: 2.0,
                18: 4.0,
                19: 2.0,
                20: 2.0,
                21: 2.0,
                23: 1.0
            })

    def test_algorithm_dijkstra_shortest_path(self):
        """
        Test Dijkstra shortest path method, weighted and non-weighted.
        """

        # Shortest path in fully directed graph
        self.assertListEqual(dijkstra_shortest_path(self.graph, 1, 28),
                             [1, 2, 3, 14, 15, 12, 13, 28])

        # Shortest path in fully directed graph considering weights
        self.assertListEqual(
            dijkstra_shortest_path(self.graph, 1, 28, weight='weight'),
            [1, 2, 3, 5, 8, 9, 12, 13, 28])

        # Reverse directionality of edge (14, 15)
        self.graph.add_edge(15, 14)
        self.graph.remove_edge(14, 15)

        self.assertListEqual(dijkstra_shortest_path(self.graph, 1, 28),
                             [1, 2, 3, 5, 8, 10, 11, 13, 28])

    def test_algorithm_dfs_paths(self):
        """
        Test depth-first search of all paths between two nodes
        """

        self.assertListEqual(
            list(dfs_paths(self.graph, 2, 26)),
            [[2, 4, 7, 25, 26], [2, 4, 5, 7, 25, 26], [2, 4, 5, 8, 10, 11, 26],
             [2, 3, 5, 7, 25, 26], [2, 3, 5, 8, 10, 11, 26]])

        # Nodes 13 and 26 not connected via directional path
        self.assertListEqual(list(dfs_paths(self.graph, 13, 26)), [])

        # Switch to breath-first search
        self.assertListEqual(
            list(dfs_paths(self.graph, 2, 26, method='bfs')),
            [[2, 4, 7, 25, 26], [2, 3, 5, 7, 25, 26], [2, 4, 5, 7, 25, 26],
             [2, 3, 5, 8, 10, 11, 26], [2, 4, 5, 8, 10, 11, 26]])

        # dfs_path with path length cutoff
        self.assertListEqual(
            list(dfs_paths(self.graph, 2, 26, cutoff=5)),
            [[2, 4, 7, 25, 26], [2, 4, 5, 7, 25, 26], [2, 3, 5, 7, 25, 26]])

    def test_algorithm_dfs_edges(self):
        """
        Test graph dfs_edges method in depth-first-search (dfs) and
        breath-first-search (bfs) mode.
        """

        self.assertListEqual(list(dfs_edges(self.graph, 5)),
                             [(5, 7), (7, 17), (17, 18), (18, 19), (18, 20),
                              (20, 21), (21, 22), (22, 23), (22, 24), (7, 25),
                              (25, 26), (26, 27), (5, 8), (8, 9), (9, 12),
                              (12, 13), (13, 28), (8, 10), (10, 11)])

        self.assertListEqual(list(dfs_edges(self.graph, 8)),
                             [(8, 9), (9, 12), (12, 13), (13, 28), (8, 10),
                              (10, 11), (11, 26), (26, 27)])

        # Breath-first search
        self.assertListEqual(list(dfs_edges(self.graph, 8, method='bfs')),
                             [(8, 9), (8, 10), (9, 12), (10, 11), (12, 13),
                              (11, 26), (13, 28), (26, 27)])

        # With depth limit
        self.assertListEqual(list(dfs_edges(self.graph, 5,
                                            max_depth=2)), [(5, 7), (7, 17),
                                                            (7, 25), (5, 8),
                                                            (8, 9), (8, 10)])

    def test_algorithm_dfs_edges__edge_based(self):
        """
        Test graph dfs_edges in True edge traversal mode
        """

        # Use true edge oriented DFS method
        self.assertListEqual(list(dfs_edges(self.graph, 8, edge_based=True)),
                             [(8, 9), (9, 12), (12, 13), (13, 28), (8, 10),
                              (10, 11), (11, 13), (11, 26), (26, 27)])

    def test_algorithm_dfs_nodes(self):
        """
        Test graph dfs_nodes method in depth-first-search (dfs) and
        breath-first-search (bfs) mode
        """

        # Connectivity information using Depth First Search / Breath first search
        self.assertListEqual(list(dfs_nodes(self.graph, 8)),
                             [8, 9, 12, 13, 28, 10, 11, 26, 27])
        self.assertListEqual(list(dfs_nodes(self.graph, 8, method='bfs')),
                             [8, 9, 10, 12, 11, 13, 26, 28, 27])

    def test_algorithm_is_reachable(self):
        """
        Test is_reachable method to test connectivity between two nodes
        """

        self.assertTrue(is_reachable(self.graph, 3, 21))

        # Reverse directionality of edge (20, 21)
        self.graph.add_edge(21, 20)
        self.graph.remove_edge(20, 21)
        self.assertFalse(is_reachable(self.graph, 7, 23))

    def test_algorithm_brandes_betweenness_centrality(self):
        """
        Test graph Brandes betweenness centrality measure
        """

        # Non-weighted Brandes betweenness centrality
        self.assertDictEqual(
            brandes_betweenness_centrality(self.graph), {
                1: 0.0,
                2: 0.038461538461538464,
                3: 0.026153846153846153,
                4: 0.04461538461538461,
                5: 0.047692307692307694,
                7: 0.08461538461538462,
                8: 0.03230769230769231,
                9: 0.00923076923076923,
                10: 0.016923076923076923,
                11: 0.013846153846153847,
                12: 0.023076923076923078,
                13: 0.01846153846153846,
                14: 0.023076923076923078,
                15: 0.01846153846153846,
                16: 0.0,
                17: 0.06461538461538462,
                18: 0.06461538461538462,
                19: 0.0,
                20: 0.04923076923076923,
                21: 0.04153846153846154,
                22: 0.03076923076923077,
                23: 0.0,
                24: 0.0,
                25: 0.01846153846153846,
                26: 0.015384615384615385,
                27: 0.0,
                28: 0.0
            })

        # Weighted Brandes betweenness centrality
        self.assertDictEqual(
            brandes_betweenness_centrality(self.graph, weight='weight'), {
                1: 0.0,
                2: 0.038461538461538464,
                3: 0.021538461538461538,
                4: 0.04923076923076923,
                5: 0.06153846153846154,
                7: 0.08461538461538462,
                8: 0.046153846153846156,
                9: 0.027692307692307693,
                10: 0.012307692307692308,
                11: 0.00923076923076923,
                12: 0.027692307692307693,
                13: 0.01846153846153846,
                14: 0.00923076923076923,
                15: 0.004615384615384615,
                16: 0.0,
                17: 0.06461538461538462,
                18: 0.06461538461538462,
                19: 0.0,
                20: 0.04923076923076923,
                21: 0.04153846153846154,
                22: 0.03076923076923077,
                23: 0.0,
                24: 0.0,
                25: 0.01846153846153846,
                26: 0.015384615384615385,
                27: 0.0,
                28: 0.0
            })

        # Non-Normalized Brandes betweenness centrality
        self.assertDictEqual(
            brandes_betweenness_centrality(self.graph, normalized=False), {
                1: 0.0,
                2: 25.0,
                3: 17.0,
                4: 29.0,
                5: 31.0,
                7: 55.0,
                8: 21.0,
                9: 6.0,
                10: 11.0,
                11: 9.0,
                12: 15.0,
                13: 12.0,
                14: 15.0,
                15: 12.0,
                16: 0.0,
                17: 42.0,
                18: 42.0,
                19: 0.0,
                20: 32.0,
                21: 27.0,
                22: 20.0,
                23: 0.0,
                24: 0.0,
                25: 12.0,
                26: 10.0,
                27: 0.0,
                28: 0.0
            })

    def test_algorithm_eigenvector_centrality(self):
        """
        Test graph node eigenvector centrality
        """

        # Default eigenvector centrality
        self.assertDictAlmostEqual(eigenvector_centrality(self.graph,
                                                          max_iter=1000),
                                   {
                                       1: 4.625586668162422e-22,
                                       2: 2.585702947502789e-19,
                                       3: 7.21415747939946e-17,
                                       4: 7.21415747939946e-17,
                                       5: 2.6788916354749308e-14,
                                       7: 3.737126037589252e-12,
                                       8: 3.723731579643154e-12,
                                       9: 4.133449353873311e-10,
                                       10: 4.133449353873311e-10,
                                       11: 3.816675918922932e-08,
                                       12: 3.8373431692993267e-08,
                                       13: 6.049668071167027e-06,
                                       14: 1.3394458408653937e-14,
                                       15: 1.861865919106721e-12,
                                       16: 1.861865919106721e-12,
                                       17: 4.152068010478676e-10,
                                       18: 3.837343162085218e-08,
                                       19: 3.0343757153351047e-06,
                                       20: 3.0343757153351047e-06,
                                       21: 0.0002095723846317974,
                                       22: 0.012842890187130716,
                                       23: 0.7070483707650801,
                                       24: 0.7070483707650801,
                                       25: 4.152068010478676e-10,
                                       26: 3.0536657740585734e-06,
                                       27: 0.00021109911510684646,
                                       28: 0.0004176371258851023
                                   },
                                   places=14)

        # Weighted eigenvector centrality
        self.assertDictAlmostEqual(eigenvector_centrality(self.graph,
                                                          max_iter=1000,
                                                          weight='weight'),
                                   {
                                       1: 8.688902566026301e-23,
                                       2: 5.899764842331867e-20,
                                       3: 2.0000289704530646e-17,
                                       4: 2.0000289704530646e-17,
                                       5: 9.026876112472413e-15,
                                       7: 1.148684996586023e-12,
                                       8: 1.5255620780686783e-12,
                                       9: 1.029772476508652e-10,
                                       10: 6.178634859047565e-10,
                                       11: 2.0822457823635333e-07,
                                       12: 6.607834043233963e-09,
                                       13: 2.131713811356956e-05,
                                       14: 9.026876112472416e-15,
                                       15: 3.051124156050468e-12,
                                       16: 1.5255620780686783e-12,
                                       17: 1.5522865250051764e-10,
                                       18: 1.745502542904305e-08,
                                       19: 3.359775472482072e-06,
                                       20: 1.679887736241036e-06,
                                       21: 0.00014125541592609745,
                                       22: 0.010542254842300024,
                                       23: 0.7070653405331172,
                                       24: 0.7070653405331172,
                                       25: 1.5522865250051764e-10,
                                       26: 2.0037291488250496e-05,
                                       27: 0.0016833983234686718,
                                       28: 0.0017929426478924984
                                   },
                                   places=14)

        # Non-convergence exception
        self.assertRaises(GraphitAlgorithmError,
                          eigenvector_centrality,
                          self.graph,
                          max_iter=100)
示例#6
0
def read_tgf(tgf, graph=None, key_tag=None):
    """
    Read graph in Trivial Graph Format
    
    TGF format dictates that nodes to be listed in the file first with each
    node on a new line. A '#' character signals the end of the node list and
    the start of the edge list.
    
    Node and edge ID's can be integers, float or strings. They are parsed
    automatically to their most likely format.
    Simple node and edge labels are supported in TGF as all characters that
    follow the node or edge ID's. They are parsed and stored in the Graph
    node and edge data stores using the graphs default or custom 'key_tag'.
    
    TGF data is imported into a default Graph object if no custom Graph
    instance is provided. The graph behaviour and the data import process is
    influenced and can be controlled using a (custom) Graph class.
    
    .. note:: TGF format always defines edges in a directed fashion.
              This is enforced even for custom graphs.
    
    :param tgf:             TGF graph data.
    :type tgf:              File, string, stream or URL
    :param graph:           Graph object to import TGF data in
    :type graph:            :graphit:Graph
    :param key_tag:         Data key to use for parsed node/edge labels.
    :type key_tag:          :py:str
    
    :return:                Graph object
    :rtype:                 :graphit:Graph
    """

    tgf_file = open_anything(tgf)
    if not isinstance(graph, Graph):
        graph = Graph()

    # Define node/edge data labels
    if key_tag:
        graph.key_tag = key_tag

    # TGF defines edges in a directed fashion. Enforce but restore later
    default_directionality = graph.directed
    graph.directed = True

    # TGF node and edge labels are unique, turn off auto_nid
    graph.auto_nid = False

    # Start parsing. First extract nodes
    nodes = True
    node_dict = {}
    for line in tgf_file.readlines():

        line = line.strip()
        if len(line):

            # Reading '#' character means switching from node
            # definition to edges
            if line.startswith('#'):
                nodes = False
                continue

            # Coarse string to types
            line = [coarse_type(n) for n in line.split()]

            # Parse nodes
            if nodes:

                attr = {}
                # Has node data
                if len(line) > 1:
                    attr = {graph.key_tag: ' '.join(line[1:])}
                nid = graph.add_node(line[0], **attr)
                node_dict[line[0]] = nid

            # Parse edges
            else:
                e1 = node_dict[line[0]]
                e2 = node_dict[line[1]]

                attr = {}
                # Has edge data
                if len(line) > 2:
                    attr = {graph.key_tag: ' '.join(line[2:])}
                graph.add_edge(e1, e2, **attr)

    tgf_file.close()

    # Restore directionality
    graph.directed = default_directionality

    return graph
class TestGraphEdgeAttribute(UnittestPythonCompatibility):
    """
    Test methods to get and set edge attributes using an edge storage driver.
    `DictStorage` is the default driver tested here which happens to be the
    same as for nodes.
    """

    def setUp(self):
        """
        Build default Graph with node and edge attributes
        """

        self.graph = Graph()
        self.graph.add_nodes([('g', {'weight': 1.0, 'value': 'gr'}), ('r', {'weight': 1.5, 'value': 'ra'}),
                              ('a', {'weight': 2.0, 'value': 'ap'}), ('p', {'weight': 2.5, 'value': 'ph'}),
                              ('h', {'weight': 3.0})])
        self.graph.add_edges([(1, 2), (2, 3), (3, 4), (3, 5), (4, 5)], value=True, weight=43.2, key='edge')

    def test_graph_edge_attr_storeget(self):
        """
        Test getting edge attributes directly from the `edges` storage
        """

        self.assertEqual(self.graph.edges[(1, 2)]['value'], True)
        self.assertEqual(self.graph.edges[(1, 2)]['weight'], 43.2)

    def test_graph_edge_attr_storeset(self):
        """
        Test setting node attributes directly from the `edges` storage
        """

        self.graph.edges[(1, 2)]['weight'] = 5.0
        self.graph.edges[(2, 3)]['value'] = 'dd'

        self.assertEqual(self.graph.edges[(1, 2)]['weight'], 5.0)
        self.assertEqual(self.graph.edges[(2, 3)]['value'], 'dd')

    def test_graph_edge_attr_key_tag(self):
        """
        Test get attributes based on `key_tag`
        """

        self.assertEqual(self.graph.edges[(1, 2)][self.graph.data.key_tag], 'edge')
        self.assertEqual(self.graph.get((1, 2)), 'edge')  # uses default node data tag

    def test_graph_edge_attr_value_tag(self):
        """
        Test get attributes based on `value_tag`
        """

        self.assertEqual(self.graph.edges[(4, 5)][self.graph.data.value_tag], True)

    def test_graph_edge_attr_dict(self):
        """
        Test if the returned full attribute dictionary is of expected format
        """

        self.assertDictEqual(self.graph.edges[(4, 5)], {'value': True, 'weight': 43.2, 'key': 'edge'})

    def test_graph_edge_attr_exception(self):
        """
        Test `edges` exception if edge not present
        """

        self.assertRaises(GraphitException, self.graph.__getitem__, (5, 6))
        self.assertIsNone(self.graph.nodes.get((5, 6)))

    def test_graph_edge_attr_graphget(self):
        """
        Test access edge attributes by nid using the (sub)graph 'get' method
        """

        self.assertEqual(self.graph.get((1, 2)), 'edge')
        self.assertEqual(self.graph.get((1, 2), 'weight'), 43.2)

        # Key does not exist
        self.assertIsNone(self.graph.get((1, 2), key='no_key'))

        # Key does not exist return defaultkey
        self.assertEqual(self.graph.get((1, 2), key='no_key', defaultattr='weight'), 43.2)

    def test_graph_edge_attr_singleedge_set(self):
        """
        Test setting edge attribute values directly using the single edge
        Graph API which has the required methods (edge_tools) added to it.
        """

        edge = self.graph.getedges((1, 2), directed=True)
        edge.weight = 4.5
        edge['key'] = 'edge_set'
        edge.set('value', False)

        self.assertEqual(edge.edges[(1, 2)]['weight'], 4.5)
        self.assertEqual(edge.edges[(1, 2)]['key'], 'edge_set')
        self.assertEqual(edge.edges[(1, 2)]['value'], False)

    def test_graph_edge_attr_singleedge_exception(self):
        """
        Test exceptions in direct access to edge attributes in a single graph
        class
        """

        edge = self.graph.getedges((1, 2), directed=True)

        self.assertEqual(edge.get(), True)
        self.assertRaises(KeyError, edge.__getitem__, 'no_key')
        self.assertRaises(AttributeError, edge.__getattr__, 'no_key')

    def test_graph_edge_attr_undirectional(self):
        """
        Undirectional edge has one attribute store
        """

        # True for DictStorage but may be different for other drivers
        self.assertEqual(id(self.graph.edges[(1, 2)]), id(self.graph.edges[(2, 1)]))

        self.assertDictEqual(self.graph.edges[(1, 2)], self.graph.edges[(2, 1)])

        self.graph.edges[(1, 2)]['key'] = 'edge_modified'
        self.assertTrue(self.graph.edges[(2, 1)]['key'] == 'edge_modified')

    def test_graph_edge_attr_directional(self):
        """
        Directional edge has two separated attribute stores
        """

        self.graph.add_edge(2, 5, directed=True, attr='to')
        self.graph.add_edge(5, 2, directed=True, attr='from')

        # True for DictStorage but may be different for other drivers
        self.assertNotEqual(id(self.graph.edges[(2, 5)]), id(self.graph.edges[(5, 2)]))

        self.assertNotEqual(self.graph.edges[(2, 5)], self.graph.edges[(5, 2)])

        self.graph.edges[(5, 2)]['attr'] = 'return'
        self.assertTrue(self.graph.edges[(2, 5)]['attr'] == 'to')
        self.assertTrue(self.graph.edges[(5, 2)]['attr'] == 'return')
示例#8
0
class TestGraphMixed(UnittestPythonCompatibility):
    """
    Test graph with mixed directed and undirected edges

        1 - 2 - 3 - 6
            | / |
            4 - 5
    """
    def setUp(self):
        """
        Build mixed directed and undirected Graph
        """

        self.graph = Graph(directed=True)
        self.graph.add_edges([(1, 2), (2, 3), (3, 2), (3, 6), (3, 5), (5, 4),
                              (4, 5), (4, 2)],
                             node_from_edge=True,
                             arg1=1.22,
                             arg2=False)
        self.graph.add_edge(3,
                            4,
                            directed=False,
                            node_from_edge=True,
                            arg1=1.22,
                            arg2=False)

        for i, edge in enumerate(self.graph.iteredges()):
            edge['nd'] = i

    def test_graph_is_mixed(self):

        self.assertTrue(self.graph.directed)
        self.assertEqual(graph_directionality(self.graph), 'mixed')
        self.assertEqual(
            sum([1 for edge in self.graph.iteredges() if edge.is_directed]), 4)
        self.assertEqual(
            sum([1 for edge in self.graph.iteredges()
                 if not edge.is_directed]), 6)
        self.assertTrue(len(self.graph.edges) == 10)

    def test_graph_contains(self):
        """
        Test a mix of directed and undirected (pairs) edges
        """

        directed = [edge.is_directed for edge in self.graph.iteredges()]
        self.assertEqual(
            directed,
            [True, False, False, False, True, True, True, False, False, False])

    def test_graph_directional_to_undirectional(self):
        """
        Test conversion of a directional to undirectional graph
        """

        undirectional = graph_directional_to_undirectional(self.graph)

        # directed attribute changed to True
        self.assertFalse(undirectional.directed)
        self.assertNotEqual(undirectional, self.graph)

        # data reference pointers determine directionality
        self.assertEqual(graph_directionality(undirectional), 'undirectional')
        self.assertEqual(
            graph_directionality(undirectional, has_data_reference=False),
            'undirectional')

        # all edges exist in pairs resulting duplicated values
        values = undirectional.edges(data='nd').values()
        self.assertEqual(len(values), len(set(values)) * 2)
class TestGraphAlgorithms(UnittestPythonCompatibility):
    def setUp(self):

        edges = {
            (5, 4): {
                'type': 'universal'
            },
            (5, 6): {
                'type': 'universal'
            },
            (11, 9): {
                'type': 'universal'
            },
            (3, 2): {
                'type': 'universal'
            },
            (2, 1): {
                'type': 'monotone'
            },
            (9, 10): {
                'type': 'universal'
            },
            (2, 3): {
                'type': 'universal'
            },
            (9, 6): {
                'type': 'universal'
            },
            (6, 5): {
                'type': 'universal'
            },
            (1, 2): {
                'type': 'monotone'
            },
            ('object', 12): {
                'type': 'universal'
            },
            (6, 9): {
                'type': 'universal'
            },
            (6, 7): {
                'type': 'universal'
            },
            (12, 13): {
                'type': 'monotone'
            },
            (7, 8): {},
            (7, 6): {
                'type': 'universal'
            },
            (13, 12): {
                'type': 'monotone'
            },
            (3, 8): {
                'type': 'universal'
            },
            (4, 5): {
                'type': 'universal'
            },
            (12, 'object'): {
                'type': 'universal'
            },
            (9, 11): {
                'type': 'universal'
            },
            (4, 3): {
                'type': 'universal'
            },
            (8, 3): {
                'type': 'universal'
            },
            (3, 4): {
                'type': 'universal'
            },
            (10, 9): {
                'type': 'universal'
            }
        }

        self.graph = Graph(auto_nid=False)
        self.graph.directed = True

        self.gn = NetworkXGraph()
        self.gn.directed = True

        self.nx = networkx.DiGraph()

        weight = 0
        for node in range(1, 14):
            self.graph.add_node(node, weight=weight)
            self.gn.add_node(node, weight=weight)
            self.nx.add_node(node, _id=node, key=node, weight=weight)
            weight += 1
        self.graph.add_node('object')
        self.gn.add_node('object')
        self.nx.add_node('object', _id=node + 1, key='object')

        weight = 0
        for eid in sorted(edges.keys(), key=lambda x: str(x[0])):
            self.graph.add_edge(*eid, weight=weight)
            self.gn.add_edge(*eid, weight=weight)
            self.nx.add_edge(*eid, weight=weight)
            weight += 0.05

    def test_graph_shortest_path_method(self):
        """
        Test Dijkstra shortest path method
        """

        from networkx.algorithms.shortest_paths.generic import shortest_path
        from networkx.algorithms.traversal.depth_first_search import dfs_preorder_nodes

        print(shortest_path(self.nx, 8, 10))
        print(list(dfs_preorder_nodes(self.nx, 8)))

        # In a mixed directed graph where 7 connects to 8 but not 8 to 7
        self.assertEqual(dijkstra_shortest_path(self.graph, 8, 10),
                         [8, 3, 4, 5, 6, 9, 10])
        self.assertEqual(list(dfs_paths(self.graph, 8, 10)),
                         [[8, 3, 4, 5, 6, 9, 10]])
        self.assertEqual(list(dfs_paths(self.graph, 8, 10, method='bfs')),
                         [[8, 3, 4, 5, 6, 9, 10]])

        # Fully connect 7 and 8
        self.graph.add_edge(8, 7, directed=True)
        self.assertEqual(dijkstra_shortest_path(self.graph, 8, 10),
                         [8, 7, 6, 9, 10])
        self.assertEqual(list(dfs_paths(self.graph, 8, 10)),
                         [[8, 7, 6, 9, 10], [8, 3, 4, 5, 6, 9, 10]])
        self.assertEqual(list(dfs_paths(self.graph, 8, 10, method='bfs')),
                         [[8, 7, 6, 9, 10], [8, 3, 4, 5, 6, 9, 10]])

    def test_graph_dfs_method(self):
        """
        Test graph depth-first-search and breath-first-search
        """

        # Connectivity information using Depth First Search / Breath first search
        self.assertListEqual(dfs(self.graph, 8),
                             [8, 3, 4, 5, 6, 9, 11, 10, 7, 2, 1])
        self.assertListEqual(dfs(self.graph, 8, method='bfs'),
                             [8, 3, 2, 4, 1, 5, 6, 7, 9, 10, 11])

    def test_graph_node_reachability_methods(self):
        """
        Test graph algorithms
        """

        # Test if node is reachable from other node (uses dfs internally)
        self.assertTrue(is_reachable(self.graph, 8, 10))
        self.assertFalse(is_reachable(self.graph, 8, 12))

    def test_graph_centrality_method(self):
        """
        Test graph Brandes betweenness centrality measure
        """

        # Return Brandes betweenness centrality
        self.assertDictEqual(
            brandes_betweenness_centrality(self.graph), {
                1: 0.0,
                2: 0.11538461538461538,
                3: 0.26282051282051283,
                4: 0.21474358974358973,
                5: 0.22756410256410256,
                6: 0.3205128205128205,
                7: 0.0673076923076923,
                8: 0.060897435897435896,
                9: 0.21794871794871795,
                10: 0.0,
                11: 0.0,
                12: 0.01282051282051282,
                13: 0.0,
                u'object': 0.0
            })

        print(brandes_betweenness_centrality(self.graph, weight='weight'))
        print(brandes_betweenness_centrality(self.graph, normalized=False))

        # Test against NetworkX if possible
        if self.nx is not None:

            from networkx.algorithms.centrality.betweenness import betweenness_centrality

            # Regular Brandes betweenness centrality
            nx_between = betweenness_centrality(self.nx)
            gn_between = brandes_betweenness_centrality(self.graph)
            self.assertDictEqual(gn_between, nx_between)

            # Weighted Brandes betweenness centrality
            nx_between = betweenness_centrality(self.nx, weight='weight')
            gn_between = brandes_betweenness_centrality(self.graph,
                                                        weight='weight')
            self.assertDictEqual(gn_between, nx_between)

            # Normalized Brandes betweenness centrality
            nx_between = betweenness_centrality(self.nx, normalized=False)
            gn_between = brandes_betweenness_centrality(self.graph,
                                                        normalized=False)
            self.assertDictEqual(gn_between, nx_between)

    def test_graph_nodes_are_interconnected(self):
        """
        Test if all nodes directly connected with one another
        """

        nodes = [1, 2, 3, 4, 5, 6]

        self.graph = Graph()
        self.graph.add_nodes(nodes)
        for edge in itertools.combinations(nodes, 2):
            self.graph.add_edge(*edge)
        self.graph.remove_edge(5, 6)

        self.assertTrue(nodes_are_interconnected(self.graph, [1, 2, 4]))
        self.assertFalse(nodes_are_interconnected(self.graph, [3, 5, 6]))

    def test_graph_degree(self):
        """
        Test (weighted) degree method
        """

        self.assertDictEqual(degree(self.graph, [1, 3, 12]), {
            1: 1,
            3: 3,
            12: 2
        })

        # Directed graphs behave the same as undirected
        self.graph.directed = False
        self.assertDictEqual(degree(self.graph, [1, 3, 12]), {
            1: 1,
            3: 3,
            12: 2
        })
        self.assertDictEqual(degree(self.graph, [1, 3, 12], weight='weight'), {
            1: 0,
            3: 1.3499999999999999,
            12: 0.35000000000000003
        })

        # Loops counted twice
        self.graph.add_edge(12, 12)
        self.assertDictEqual(degree(self.graph, [1, 3, 12]), {
            1: 1,
            3: 3,
            12: 4
        })
        self.assertDictEqual(degree(self.graph, [1, 3, 12], weight='weight'), {
            1: 0,
            3: 1.3499999999999999,
            12: 2.3499999999999996
        })
示例#10
0
def read_p2g(p2g_file, graph=None):
    """
    Read graph in P2G format

    :param p2g_file:      P2G data to parse
    :type p2g_file:       File, string, stream or URL
    :param graph:         Graph object to import to or Graph by default
    :type graph:          :graphit:Graph

    :return:              Graph instance
    :rtype:               :graphit:Graph
    """

    p2g_file = open_anything(p2g_file)

    if graph is None:
        graph = Graph()
    elif not isinstance(graph, Graph):
        raise GraphitException('Unsupported graph type {0}'.format(
            type(graph)))

    # P2G graphs are directed
    graph.directed = True

    graph_name = None
    graph_layout = None
    curr_node = None
    nodes = {}
    for i, line in enumerate(p2g_file.readlines()):

        line = line.strip()
        if line:

            # Parse p2g graph name (first line)
            sline = line.split()
            if not graph_name:
                graph_name = line
                continue

            # Parse number of nodes and edges (second line)
            elif not graph_layout:
                try:
                    graph_layout = map(int, sline)
                except ValueError:
                    raise GraphitException(
                        'P2G import error: line {0} - {1}'.format(i, line))
                continue

            # Parse nodes and edges
            if len(sline) == 1:
                nodes[line] = []
                curr_node = line
            elif len(sline) == 2:
                try:
                    nodes[curr_node] = map(int, sline)
                except ValueError:
                    raise GraphitException(
                        'P2G import error: malformed edge on line {0} - {1}'.
                        format(i, line))
            else:
                raise GraphitException(
                    'P2G import error: line {0} - {1}'.format(i, line))

    graph.data['name'] = graph_name

    # Add nodes
    mapped_nodes = graph.add_nodes(nodes.keys())

    # Add edges
    for i, nid in enumerate(nodes.keys()):
        for e in nodes[nid]:
            if e < len(mapped_nodes):
                graph.add_edge(mapped_nodes[i], mapped_nodes[e])
            else:
                raise GraphitException(
                    'P2G import error: edge node index {0} not in graph'.
                    format(e))

    if len(nodes) != graph_layout[0] or (len(graph.edges)) != graph_layout[1]:
        logging.warning(
            'P2G import warning: declared number of nodes and edges {0}-{1} does not match {2}-{3}'
            .format(graph_layout[0], graph_layout[1], len(nodes),
                    len(graph.edges)))

    return graph
示例#11
0
def read_lgr(lgr, graph=None, edge_label='label'):
    """
    Read graph in LEDA format

    Nodes are added to the graph using a unique ID or with the node data
    as label depending if the graph.data.auto_nid is True or False.
    Edge data is added to the edge attributes using `edge_label` as key.
    The data types for both nodes and edges is set according to the
    specifications in the LEDA header as either string, int, float or bool.

    :param lgr:             LEDA graph data.
    :type lgr:              File, string, stream or URL
    :param graph:           Graph object to import LEDA data in
    :type graph:            :graphit:Graph
    :param edge_label:      edge data label name
    :type edge_label:       :py:str

    :return:                Graph object
    :rtype:                 :graphit:Graph
    :raises:                TypeError if node/edge type conversion failed
                            GraphitException in case of malformed LEDA file
    """

    # User defined or default Graph object
    if graph is None:
        graph = Graph()
    elif not isinstance(graph, Graph):
        raise GraphitException('Unsupported graph type {0}'.format(
            type(graph)))

    # Parse LEDA file
    lgr_file = open_anything(lgr)
    header = []
    nodes = []
    edges = []
    container = header
    for line in lgr_file.readlines():
        line = line.strip()

        if line:
            if line.startswith('#header'):
                container = header
                continue
            if line.startswith('#nodes'):
                container = nodes
                continue
            if line.startswith('#edges'):
                container = edges
                continue

            container.append(line)

    # Parse LEDA header
    if not header[0] == 'LEDA.GRAPH':
        raise GraphitException('File is not a valid LEDA graph format')

    # Node and edge data types and graph directionality
    node_type = data_types.get(header[1])
    edge_type = data_types.get(header[2])
    graph.directed = int(header[3]) == -1

    # Parse LEDA nodes
    node_mapping = {}
    for i, node in enumerate(nodes[1:], start=1):
        data = node.strip('|{}|') or None
        if node_type and data:
            data = node_type(data)
        nid = graph.add_node(data)
        node_mapping[i] = nid

    # Parse LEDA edges
    for edge in edges[1:]:
        try:
            source, target, reversal, label = edge.split()
        except ValueError:
            raise GraphitException(
                'Too few fields in LEDA edge {0}'.format(edge))

        attr = {edge_label: label.strip('|{}|') or None}
        if edge_type and attr[edge_label]:
            attr[edge_label] = edge_type(attr[edge_label])
        graph.add_edge(node_mapping[int(source)], node_mapping[int(target)],
                       **attr)

    return graph
class TestGraphAddNodeConnected(UnittestPythonCompatibility):
    """
    Test add_connect method for direct addition and edge connection of a new
    node to an existing node using a single node object
    """
    currpath = os.path.dirname(__file__)

    def setUp(self):
        """
        Build empty graph to add a node to and test default state
        """

        self.graph = Graph(auto_nid=False)

        # Add two nodes
        self.graph.add_nodes(('one', 'two'))
        self.graph.add_edge('one', 'two')

        # Two nodes and one edge
        self.assertTrue(len(self.graph) == 2)
        self.assertTrue(len(self.graph.nodes) == 2)
        self.assertTrue(len(self.graph.edges) == 2)
        self.assertTrue(len(self.graph.adjacency) == 2)

        # auto_nid
        self.assertFalse(self.graph.data.auto_nid)

    def tearDown(self):
        """
        Test state after node addition
        """

        nids = sorted(self.graph.nodes)

        # The nid should equal the node
        self.assertTrue(self.node in nids)

        # The _id is still set
        self.assertEqual(self.graph.nodes[self.node]['_id'], 3)
        self.assertEqual(self.graph.data.nodeid, 4)

        # filled after addition
        self.assertTrue(len(self.graph) == 3)
        self.assertTrue(len(self.graph.nodes) == 3)
        self.assertTrue(len(self.graph.edges) == 4)
        self.assertTrue(len(self.graph.adjacency) == 3)

        # no adjacency
        self.assertTrue(len(self.graph.adjacency[nids[0]]) == 1)

    def test_add_connect_string(self):
        """
        Test add connect a string node
        """

        self.node = 'three'

        node = self.graph.getnodes('two')
        node.add_connect(self.node)

        self.assertTrue(('two', 'three') in self.graph.edges)
        self.assertTrue(('three', 'two') in self.graph.edges)

    def test_add_connect_attr(self):
        """
        Test add connect a node with node and edge attributes
        """

        self.node = 'three'

        node = self.graph.getnodes('two')
        node.add_connect(self.node,
                         node_kwargs={
                             'arg': True,
                             'n': 1.22
                         },
                         edge_kwargs={
                             'arg': True,
                             'e': 5.44
                         })

        # Node should contain keyword arguments
        self.assertTrue(self.graph.nodes[self.node]['arg'])
        self.assertTrue(self.graph.nodes[self.node]['n'] == 1.22)

        # Edges should contain keyword arguments
        edge = self.graph.getedges(('two', self.node))
        self.assertTrue(all(e.get('arg', False) for e in edge.edges.values()))
        self.assertTrue(all(e.get('e') == 5.44 for e in edge.edges.values()))
示例#13
0
def read_gexf(gexf_file, graph=None):
    """
    Read graphs in GEXF format

    Uses the Python build-in etree cElementTree parser to parse the XML
    document and convert the elements into nodes.
    The XML element tag becomes the node key, XML text becomes the node
    value and XML attributes are added to the node as additional attributes.

    :param gexf_file:      XML data to parse
    :type gexf_file:       File, string, stream or URL
    :param graph:          Graph object to import dictionary data in
    :type graph:           :graphit:Graph

    :return:               GraphAxis object
    :rtype:                :graphit:GraphAxis
    """

    gexf_file = open_anything(gexf_file)

    # User defined or default Graph object
    if graph is None:
        graph = Graph()
    elif not isinstance(graph, Graph):
        raise GraphitException('Unsupported graph type {0}'.format(
            type(graph)))

    # Try parsing the string using default Python cElementTree parser
    try:
        tree = et.fromstring(gexf_file.read())
    except et.ParseError as error:
        logging.error(
            'Unable to parse GEXF file. cElementTree error: {0}'.format(error))
        return

    # Get XMLNS namespace from root
    xmlns = None
    for elem in tree.iter():
        if elem.tag.endswith('gexf'):
            xmlns = elem.tag.split('}')[0] + '}'
            break

    if xmlns is None:
        raise GraphitException(
            'Invalid GEXF file format, "gexf" tag not found')

    # Add graph meta-data and XMLNS namespace
    for meta in tree.iter('{0}meta'.format(xmlns)):
        graph.data.update(meta.attrib)
        for meta_data in meta:
            tag = meta_data.tag.split('}')[1]
            graph.data[tag] = meta_data.text

    # GEXF node and edge labels are unique, turn off auto_nid
    graph.data['auto_nid'] = False

    graph_tag = tree.find('{0}graph'.format(xmlns))
    graph.directed = graph_tag.get('defaultedgetype', 'directed') == 'directed'
    graph.data.update(graph_tag.attrib)

    # Parse all nodes
    nodes = tree.findall('.//{0}node'.format(xmlns))
    if not len(nodes):
        raise GraphitException('GEXF file containes no "node" elements')
    for node in nodes:
        attr = node.attrib
        attr = parse_attvalue_elements(node, attr, xmlns=xmlns)
        graph.add_node(attr['id'],
                       **dict([n for n in attr.items() if n[0] != 'id']))

    # Parse all edges
    edges = tree.findall('.//{0}edge'.format(xmlns))
    for edge in edges:
        attr = edge.attrib

        # Edge direction differs from global graph directionality
        edge_directed = graph.directed
        if 'type' in attr:
            edge_directed = attr['type'] == 'directed'

        attr = parse_attvalue_elements(edge, attr, xmlns=xmlns)
        graph.add_edge(attr['source'],
                       attr['target'],
                       directed=edge_directed,
                       **dict([
                           n for n in attr.items()
                           if n[0] not in ('source', 'target')
                       ]))

    logger.info('Import graph in GEXF format. XMLNS: {0}'.format(xmlns))

    return graph