graph

class Graph:
    def __init__(self, nrVertices):
        self._dictOut =  {}
        self._dictIn =  {}
        self._nrVertices = nrVertices
        for x in range(nrVertices):
            self._dictOut[x] = []
            self._dictIn[x] = []

    def get_nr_vertices(self):
        return self._nrVertices


    def get_dict_keys(self):
        return self._dictOut.keys()


    def add_vertex(self, vertex):
        self._dictOut[vertex] = []
        self._dictIn[vertex] = []
        self._nrVertices += 1


    def remove_vertex(self, vertex):
        removed = []
        for x in self._dictOut[vertex]:
            removed.append((vertex, x))
            self._dictIn[x].remove(vertex)
        for x in self._dictIn[vertex]:
            removed.append((x, vertex))
            self._dictOut[x].remove(vertex)

        del self._dictOut[vertex]
        del self._dictIn[vertex]
        self._nrVertices -= 1
        return removed


    def add_edge(self, start_vertex, end_vertex):
        if end_vertex not in self._dictOut[start_vertex]:
            self._dictOut[start_vertex].append(end_vertex)

        if start_vertex not in self._dictIn[end_vertex]:
            self._dictIn[end_vertex].append(start_vertex)


    def remove_edge(self, start_vertex, end_vertex):
        self._dictOut[start_vertex].remove(end_vertex)
        self._dictIn[end_vertex].remove(start_vertex)

    def is_edge(self, start_vertex, end_vertex):
        if end_vertex in self._dictOut[start_vertex]:
            return True
        return False

    def vertex_degree(self, vertex):
        return [len(self._dictIn[vertex]), len(self._dictOut[vertex])]

    def outbound(self, vertex):
        return self._dictOut[vertex]

    def inbound(self, vertex):
        return self._dictIn[vertex]

    def __str__(self):
        message = "Outbound\n"
        new_dict = self._dictOut.items()
        for k, v in new_dict:
            message += str(k) + ":" + str(v) + "\n"
        message += "Inbound\n"
        new_dict = self._dictIn.items()
        for k, v in new_dict:
            message += str(k) + ":" + str(v) + "\n"
        return message