Pure python methods for modelling simple graphs and building a set of disjoint graphs edge by ende

graph_set.py

class Graph(object):
    def __init__(self, nodes, edges=None):
        self.nodes = nodes
        self.edges = set()
        self.add_edges(edges or set())

    def __hash__(self):
        return hash(frozenset(self.edges)) + hash(frozenset(self.nodes))
    
    def __repr__(self):
        return 'Graph(nodes={}, edges={})'.format(self.nodes, self.edges)
    
    def add_directed_edge(self, from_node, to_node):
        hash(from_node)
        hash(to_node)
        if from_node not in self.nodes and to_node not in self.nodes:
            raise ValueError('Neither node in graph')
        self.nodes.add(from_node)
        self.nodes.add(to_node)
        self.edges.add((from_node, to_node))        
        
    def add_undirected_edge(self, from_node, to_node):
        self.add_directed_edge(from_node, to_node)
        self.add_directed_edge(to_node, from_node)
        
    def add_edges(self, edges):
        for from_node, to_node in edges:
            self.add_directed_edge(from_node, to_node)

    def update(self, graph):
        self.nodes |= graph.nodes
        self.add_edges(graph.edges)

class GraphSet(object):
    def __init__(self):
        self.graphs = {}
    
    def add_directed_edge(self, from_node, to_node):
        from_node_graph = self.graphs.get(from_node) or Graph({from_node})
        to_node_graph = self.graphs.get(to_node) or Graph({to_node})
        from_node_graph.add_directed_edge(from_node, to_node)
        if id(from_node_graph) == id(to_node_graph):
            return
        if hash(from_node_graph) != hash(to_node_graph):
            from_node_graph.update(to_node_graph)
        for k in from_node_graph.nodes:
            self.graphs[k] = from_node_graph        
        
    def add_undirected_edge(self, from_node, to_node):
        self.add_directed_edge(from_node, to_node)
        self.add_directed_edge(to_node, from_node)
    
    def unique(self):
        return set(self.graphs.values())
    
    def __len__(self):
        return len(self.graphs)