transforms.py 文件源码

def add_edge(self, u, v, *args, **kwargs):
        changed = False
        if u == v:
            if self.flags['strict']:
                raise ValueError('Edge must be between two unique nodes!')
            return changed
        if self._undirected.has_edge(u, v):
            self.remove_edges_from([[u, v], [v,u]])
        elif len(self.nodes()) > 0:
            try: 
                path = nx.shortest_path(self._undirected, u, v)
                if self.flags['strict']:
                    raise ValueError('Multiple edge path exists between nodes!')
                self.disconnect_path(path)
                changed = True
            except (nx.NetworkXError, nx.NetworkXNoPath):
                pass
        self._undirected.add_edge(u,v)
        super(self.__class__, self).add_edge(u, v, *args, **kwargs)

        if self.flags['assert_forest']:
            # this is quite slow but makes very sure structure is correct 
            # so is mainly used for testing
            assert nx.is_forest(nx.Graph(self))

        return changed