Python heap optimize dijkstra algorithm

gistfile1.py

import sys
from heapq import heappush, heappop

class Dijkstra:
    def __init__(self, adjacents):
        self.adj = adjacents
        self.n = len(adjacents)

    def dijkstra(self, start):
        dis, vis, hq = {}, {}, []

        for node in self.adj.keys():
            dis[node] = sys.maxint
            vis[node] = False

        dis[start], vis[start] = 0, True
        heappush(hq, (0, start))

        while hq:
            (d, node) = heappop(hq)
            vis[node] = True

            for n, weight in self.adj[node].items():
                if (not vis[n]) and (d + weight < dis[n]):
                    dis[n] = d + weight
                    heappush(hq, (dis[n], n))

        return dis


G = {'s':{'u':10, 'x':5},
     'u':{'v':1, 'x':2},
     'v':{'y':4},
     'x':{'u':3, 'v':9, 'y':2},
     'y':{'s':7, 'v':6}}


if __name__ == '__main__':
    d = Dijkstra(G)
    print d.dijkstra('s')
    print d.dijkstra('u')
    print d.dijkstra('x')

I guess the time complexity is still VE complete graph it will be V^2