511 lines
12 KiB
Python
511 lines
12 KiB
Python
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#!/usr/bin/env python
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# -*- coding: utf-8 -*-
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#
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# Licensed under the GNU LGPL v2.1 - http://www.gnu.org/licenses/lgpl.html
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"""This module contains abstract class IGraph represents graphs interface and
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class Graph (based on IGraph) which implements undirected graph.
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Examples
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--------
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Create simple graph with 4 nodes.
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>>> g = Graph()
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>>> g.add_node('Felidae')
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>>> g.add_node('Lion')
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>>> g.add_node('Tiger')
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>>> g.add_node('Wolf')
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>>> sorted(g.nodes())
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['Felidae', 'Lion', 'Tiger', 'Wolf']
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Add some edges and check neighbours.
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>>> g.add_edge(("Felidae", "Lion"))
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>>> g.add_edge(("Felidae", "Tiger"))
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>>> g.neighbors("Felidae")
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['Lion', 'Tiger']
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One node has no neighbours.
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>>> g.neighbors("Wolf")
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[]
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"""
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from abc import ABCMeta, abstractmethod
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class IGraph(object):
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"""Represents the interface or contract that the graph for TextRank
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should implement.
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"""
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__metaclass__ = ABCMeta
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@abstractmethod
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def nodes(self):
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"""Returns all nodes of graph.
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Returns
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-------
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list of hashable
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Nodes of graph.
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"""
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pass
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@abstractmethod
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def edges(self):
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"""Returns all edges of graph.
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Returns
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-------
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list of (hashable, hashable)
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Edges of graph.
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"""
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pass
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@abstractmethod
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def neighbors(self, node):
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"""Return all nodes that are directly accessible from given node.
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Parameters
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----------
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node : hashable
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Given node identifier.
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Returns
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-------
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list of hashable
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Nodes directly accessible from given `node`.
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"""
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pass
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@abstractmethod
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def has_node(self, node):
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"""Returns whether the requested node exists.
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Parameters
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----------
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node : hashable
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Given node identifier.
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Returns
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-------
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bool
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True if `node` exists, False otherwise.
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"""
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pass
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@abstractmethod
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def add_node(self, node, attrs=None):
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"""Adds given node to the graph.
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Note
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----
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While nodes can be of any type, it's strongly recommended to use only numbers and single-line strings
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as node identifiers if you intend to use write().
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Parameters
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----------
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node : hashable
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Given node
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attrs : list, optional
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Node attributes specified as (attribute, value)
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"""
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pass
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@abstractmethod
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def add_edge(self, edge, wt=1, label='', attrs=None):
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"""Adds an edge to the graph connecting two nodes. An edge, here,
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is a tuple of two nodes.
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Parameters
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----------
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edge : (hashable, hashable)
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Given edge.
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wt : float, optional
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Weight of new edge.
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label : str, optional
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Edge label.
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attrs : list, optional
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Node attributes specified as (attribute, value)
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"""
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pass
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@abstractmethod
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def has_edge(self, edge):
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"""Returns whether an edge exists.
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Parameters
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----------
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edge : (hashable, hashable)
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Given edge.
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Returns
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-------
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bool
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True if `edge` exists, False otherwise.
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"""
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pass
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@abstractmethod
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def edge_weight(self, edge):
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"""Returns weigth of given edge.
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Parameters
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----------
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edge : (hashable, hashable)
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Given edge.
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Returns
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-------
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float
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Edge weight.
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"""
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pass
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@abstractmethod
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def del_node(self, node):
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"""Removes node and its edges from the graph.
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Parameters
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----------
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node : hashable
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Node to delete.
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"""
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pass
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class Graph(IGraph):
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"""
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Implementation of an undirected graph, based on IGraph.
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Attributes
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----------
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Graph.WEIGHT_ATTRIBUTE_NAME : str
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Name of weight attribute in graph.
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Graph.DEFAULT_WEIGHT : float
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Weight set by default.
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Graph.LABEL_ATTRIBUTE_NAME : str
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Default name of attribute. Not used.
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Graph.DEFAULT_LABEL : str
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Label set by default. Not used.
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"""
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WEIGHT_ATTRIBUTE_NAME = "weight"
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DEFAULT_WEIGHT = 0
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LABEL_ATTRIBUTE_NAME = "label"
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DEFAULT_LABEL = ""
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def __init__(self):
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"""Initializes object."""
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# Metadata about edges
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# Mapping: Edge -> Dict mapping, lablel-> str, wt->num
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self.edge_properties = {}
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# Key value pairs: (Edge -> Attributes)
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self.edge_attr = {}
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# Metadata about nodes
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# Pairing: Node -> Attributes
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self.node_attr = {}
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# Pairing: Node -> Neighbors
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self.node_neighbors = {}
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def has_edge(self, edge):
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"""Returns whether an edge exists.
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Parameters
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----------
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edge : (hashable, hashable)
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Given edge.
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Returns
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-------
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bool
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True if `edge` exists, False otherwise.
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"""
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u, v = edge
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return (u, v) in self.edge_properties and (v, u) in self.edge_properties
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def edge_weight(self, edge):
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"""Returns weight of given edge.
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Parameters
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----------
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edge : (hashable, hashable)
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Given edge.
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Returns
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-------
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float
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Edge weight.
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"""
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return self.get_edge_properties(edge).setdefault(self.WEIGHT_ATTRIBUTE_NAME, self.DEFAULT_WEIGHT)
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def neighbors(self, node):
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"""Returns all nodes that are directly accessible from given node.
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Parameters
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----------
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node : hashable
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Given node identifier.
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Returns
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-------
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list of hashable
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Nodes directly accessible from given `node`.
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"""
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return self.node_neighbors[node]
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def has_node(self, node):
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"""Returns whether the requested node exists.
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Parameters
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----------
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node : hashable
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Given node.
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Returns
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-------
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bool
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True if `node` exists, False otherwise.
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"""
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return node in self.node_neighbors
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def add_edge(self, edge, wt=1, label='', attrs=None):
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"""Adds an edge to the graph connecting two nodes.
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Parameters
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----------
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edge : (hashable, hashable)
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Given edge.
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wt : float, optional
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Weight of new edge.
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label : str, optional
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Edge label.
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attrs : list, optional
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Node attributes specified as (attribute, value).
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Raises
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------
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ValueError
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If `edge` already exists in graph.
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"""
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if attrs is None:
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attrs = []
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u, v = edge
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if v not in self.node_neighbors[u] and u not in self.node_neighbors[v]:
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self.node_neighbors[u].append(v)
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if u != v:
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self.node_neighbors[v].append(u)
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self.add_edge_attributes((u, v), attrs)
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self.set_edge_properties((u, v), label=label, weight=wt)
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else:
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raise ValueError("Edge (%s, %s) already in graph" % (u, v))
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def add_node(self, node, attrs=None):
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"""Adds given node to the graph.
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Note
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----
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While nodes can be of any type, it's strongly recommended
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to use only numbers and single-line strings as node identifiers if you
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intend to use write().
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Parameters
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----------
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node : hashable
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Given node.
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attrs : list of (hashable, hashable), optional
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Node attributes specified as (attribute, value)
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Raises
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------
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ValueError
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If `node` already exists in graph.
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"""
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if attrs is None:
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attrs = []
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if node not in self.node_neighbors:
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self.node_neighbors[node] = []
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self.node_attr[node] = attrs
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else:
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raise ValueError("Node %s already in graph" % node)
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def nodes(self):
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"""Returns all nodes of the graph.
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Returns
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-------
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list of hashable
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Nodes of graph.
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"""
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return list(self.node_neighbors.keys())
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def edges(self):
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"""Returns all edges of the graph.
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Returns
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-------
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list of (hashable, hashable)
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Edges of graph.
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"""
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return [a for a in self.edge_properties.keys()]
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def del_node(self, node):
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"""Removes given node and its edges from the graph.
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Parameters
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----------
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node : hashable
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Given node.
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"""
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for each in list(self.neighbors(node)):
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if each != node:
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self.del_edge((each, node))
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del self.node_neighbors[node]
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del self.node_attr[node]
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def get_edge_properties(self, edge):
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"""Returns properties of given given edge. If edge doesn't exist
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empty dictionary will be returned.
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Parameters
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----------
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edge : (hashable, hashable)
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Given edge.
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Returns
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-------
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dict
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Properties of graph.
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"""
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return self.edge_properties.setdefault(edge, {})
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def add_edge_attributes(self, edge, attrs):
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"""Adds attributes `attrs` to given edge, order of nodes in edge doesn't matter.
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Parameters
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----------
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edge : (hashable, hashable)
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Given edge.
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attrs : list
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Provided attributes to add.
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"""
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for attr in attrs:
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self.add_edge_attribute(edge, attr)
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def add_edge_attribute(self, edge, attr):
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"""Adds attribute `attr` to given edge, order of nodes in edge doesn't matter.
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Parameters
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----------
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edge : (hashable, hashable)
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Given edge.
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attr : object
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Provided attribute to add.
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"""
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self.edge_attr[edge] = self.edge_attributes(edge) + [attr]
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if edge[0] != edge[1]:
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self.edge_attr[(edge[1], edge[0])] = self.edge_attributes((edge[1], edge[0])) + [attr]
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def edge_attributes(self, edge):
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"""Returns attributes of given edge.
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Note
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----
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In case of non existing edge returns empty list.
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Parameters
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----------
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edge : (hashable, hashable)
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Given edge.
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Returns
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-------
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|
list
|
||
|
|
Attributes of given edge.
|
||
|
|
|
||
|
|
"""
|
||
|
|
try:
|
||
|
|
return self.edge_attr[edge]
|
||
|
|
except KeyError:
|
||
|
|
return []
|
||
|
|
|
||
|
|
def set_edge_properties(self, edge, **properties):
|
||
|
|
"""Adds `properties` to given edge, order of nodes in edge doesn't matter.
|
||
|
|
|
||
|
|
Parameters
|
||
|
|
----------
|
||
|
|
edge : (hashable, hashable)
|
||
|
|
Given edge.
|
||
|
|
|
||
|
|
properties : dict
|
||
|
|
Properties to add.
|
||
|
|
|
||
|
|
"""
|
||
|
|
self.edge_properties.setdefault(edge, {}).update(properties)
|
||
|
|
if edge[0] != edge[1]:
|
||
|
|
self.edge_properties.setdefault((edge[1], edge[0]), {}).update(properties)
|
||
|
|
|
||
|
|
def del_edge(self, edge):
|
||
|
|
"""Removes given edges from the graph.
|
||
|
|
|
||
|
|
Parameters
|
||
|
|
----------
|
||
|
|
edge : (hashable, hashable)
|
||
|
|
Given edge.
|
||
|
|
|
||
|
|
"""
|
||
|
|
u, v = edge
|
||
|
|
self.node_neighbors[u].remove(v)
|
||
|
|
self.del_edge_labeling((u, v))
|
||
|
|
if u != v:
|
||
|
|
self.node_neighbors[v].remove(u)
|
||
|
|
self.del_edge_labeling((v, u))
|
||
|
|
|
||
|
|
def del_edge_labeling(self, edge):
|
||
|
|
"""Removes attributes and properties of given edge.
|
||
|
|
|
||
|
|
Parameters
|
||
|
|
----------
|
||
|
|
edge : (hashable, hashable)
|
||
|
|
Given edge.
|
||
|
|
|
||
|
|
"""
|
||
|
|
keys = [edge, edge[::-1]]
|
||
|
|
|
||
|
|
for key in keys:
|
||
|
|
for mapping in [self.edge_properties, self.edge_attr]:
|
||
|
|
try:
|
||
|
|
del mapping[key]
|
||
|
|
except KeyError:
|
||
|
|
pass
|