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opt
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imh-python
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lib
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python3.9
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site-packages
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pygraph
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classes
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/opt/imh-python/lib/python3.9/site-packages/pygraph/classes
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__pycache__/
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directed_graph.py
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undirected_graph.py
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__init__.py
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/opt/imh-python/lib/python3.9/site-packages/pygraph/classes/directed_graph.py
(7612B)
"""Implements the functionality of a directed graph.""" import copy from ..exceptions import NonexistentNodeError, NonexistentEdgeError class DirectedGraph(object): nodes = None edges = None next_node_id = 1 next_edge_id = 1 def __init__(self): self.nodes = {} self.edges = {} self._num_nodes = 0 self._num_edges = 0 def __deepcopy__(self, memo=None): graph = DirectedGraph() graph.nodes = copy.deepcopy(self.nodes) graph.edges = copy.deepcopy(self.edges) graph.next_node_id = self.next_node_id graph.next_edge_id = self.next_edge_id graph._num_nodes = self._num_nodes graph._num_edges = self._num_edges return graph def num_nodes(self): """Returns the current number of nodes in the graph.""" return self._num_nodes def num_edges(self): """Returns the current number of edges in the graph.""" return self._num_edges def generate_node_id(self): node_id = self.next_node_id self.next_node_id += 1 return node_id def generate_edge_id(self): edge_id = self.next_edge_id self.next_edge_id += 1 return edge_id def new_node(self): """Adds a new, blank node to the graph. Returns the node id of the new node.""" node_id = self.generate_node_id() node = {'id': node_id, 'edges': [], 'data': {} } self.nodes[node_id] = node self._num_nodes += 1 return node_id def new_edge(self, node_a, node_b, cost=1): """Adds a new edge from node_a to node_b that has a cost. Returns the edge id of the new edge.""" # Verify that both nodes exist in the graph try: self.nodes[node_a] except KeyError: raise NonexistentNodeError(node_a) try: self.nodes[node_b] except KeyError: raise NonexistentNodeError(node_b) # Create the new edge edge_id = self.generate_edge_id() edge = {'id': edge_id, 'vertices': (node_a, node_b), 'cost': cost, 'data': {} } self.edges[edge_id] = edge self.nodes[node_a]['edges'].append(edge_id) self._num_edges += 1 return edge_id def neighbors(self, node_id): """Find all the nodes where there is an edge from the specified node to that node. Returns a list of node ids.""" node = self.get_node(node_id) return [self.get_edge(edge_id)['vertices'][1] for edge_id in node['edges']] def adjacent(self, node_a, node_b): """Determines whether there is an edge from node_a to node_b. Returns True if such an edge exists, otherwise returns False.""" neighbors = self.neighbors(node_a) return node_b in neighbors def edge_cost(self, node_a, node_b): """Returns the cost of moving between the edge that connects node_a to node_b. Returns +inf if no such edge exists.""" cost = float('inf') node_object_a = self.get_node(node_a) for edge_id in node_object_a['edges']: edge = self.get_edge(edge_id) tpl = (node_a, node_b) if edge['vertices'] == tpl: cost = edge['cost'] break return cost def get_node(self, node_id): """Returns the node object identified by "node_id".""" try: node_object = self.nodes[node_id] except KeyError: raise NonexistentNodeError(node_id) return node_object def get_all_node_ids(self): """Returns a list of all the node ids in the graph.""" return list(self.nodes.keys()) def get_all_node_objects(self): """Returns a list of all the node objects in the graph.""" return list(self.nodes.values()) def get_edge(self, edge_id): """Returns the edge object identified by "edge_id".""" try: edge_object = self.edges[edge_id] except KeyError: raise NonexistentEdgeError(edge_id) return edge_object def get_all_edge_ids(self): """Returns a list of all the edge ids in the graph""" return list(self.edges.keys()) def get_all_edge_objects(self): """Returns a list of all the edge objects in the graph.""" return list(self.edges.values()) def delete_edge_by_id(self, edge_id): """Removes the edge identified by "edge_id" from the graph.""" edge = self.get_edge(edge_id) # Remove the edge from the "from node" # --Determine the from node from_node_id = edge['vertices'][0] from_node = self.get_node(from_node_id) # --Remove the edge from it from_node['edges'].remove(edge_id) # Remove the edge from the edge list del self.edges[edge_id] self._num_edges -= 1 def delete_edge_by_nodes(self, node_a, node_b): """Removes all the edges from node_a to node_b from the graph.""" node = self.get_node(node_a) # Determine the edge ids edge_ids = [] for e_id in node['edges']: edge = self.get_edge(e_id) if edge['vertices'][1] == node_b: edge_ids.append(e_id) # Delete the edges for e in edge_ids: self.delete_edge_by_id(e) def delete_node(self, node_id): """Removes the node identified by node_id from the graph.""" node = self.get_node(node_id) # Remove all edges from the node for e in node['edges']: self.delete_edge_by_id(e) # Remove all edges to the node edges = [edge_id for edge_id, edge in list(self.edges.items()) if edge['vertices'][1] == node_id] for e in edges: self.delete_edge_by_id(e) # Remove the node from the node list del self.nodes[node_id] self._num_nodes -= 1 def move_edge_source(self, edge_id, node_a, node_b): """Moves an edge originating from node_a so that it originates from node_b.""" # Grab the edge edge = self.get_edge(edge_id) # Alter the vertices edge['vertices'] = (node_b, edge['vertices'][1]) # Remove the edge from node_a node = self.get_node(node_a) node['edges'].remove(edge_id) # Add the edge to node_b node = self.get_node(node_b) node['edges'].append(edge_id) def move_edge_target(self, edge_id, node_a): """Moves an edge so that it targets node_a.""" # Grab the edge edge = self.get_edge(edge_id) # Alter the vertices edge['vertices'] = (edge['vertices'][0], node_a) def get_edge_ids_by_node_ids(self, node_a, node_b): """Returns a list of edge ids connecting node_a to node_b.""" # Check if the nodes are adjacent if not self.adjacent(node_a, node_b): return [] # They're adjacent, so pull the list of edges from node_a and determine which ones point to node_b node = self.get_node(node_a) return [edge_id for edge_id in node['edges'] if self.get_edge(edge_id)['vertices'][1] == node_b] def get_first_edge_id_by_node_ids(self, node_a, node_b): """Returns the first (and possibly only) edge connecting node_a and node_b.""" ret = self.get_edge_ids_by_node_ids(node_a, node_b) if not ret: return None else: return ret[0]
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