text: import heapq
  
  
  class PriorityQueue(object):
  
      def __init__(self):
          self._queue = []
          self._index = 0
  
      def __len__(self):
          return len(self._queue)
  
      def push(self, item, priority):
          setattr(item, '_heapindex', self._index)
          heapq.heappush(self._queue, (-priority, self._index, item))
          self._update_index()
          self._index += 1
  
      def pop(self):
          el = heapq.heappop(self._queue)[-1]
          el._heapindex = -1
          self._update_index()
          return el
  
      def front(self):
          return self._queue[0][-1]
  
      def _update_index(self):
          if self._queue:
              for i, el in enumerate(zip(*self._queue)[2]):
                  el._heapindex = i
  
  