2.13_graph_图

class Graph(object):

    def __init__(self, gdict=None):
        if gdict is None:
            gdict = {}
        self.gdict = gdict

    def edges(self):
        return self.get_edges()

    def get_vertices(self):
        """get the keys of gdict"""

        return list(self.gdict.keys())

    def get_edges(self):
        """get distinct list of edges"""

        edge_list = []

        for v in self.gdict:
            for nxt_v in self.gdict[v]:
                if {v, nxt_v} not in edge_list:
                    edge_list.append({v, nxt_v})

        return edge_list

    def add_vertex(self, vertex):

        if vertex not in self.gdict:
            self.gdict[vertex] = []

    def add_edge(self, edge):

        edge = set(edge)
        (v1, v2) = tuple(edge)
        if v1 in self.gdict:
            self.gdict[v1].append(v2)
        else:
            self.gdict[v1] = [v2]


g_element = {'a':['b','c'],'b':['a','d'],'c':['a','d'],'d':['e'],'e':['d']}
g = Graph(g_element)
g.add_edge({'a','e'})
g.add_edge({'a','c'})
print(g.edges())