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Priority Queue Dictionary (pqdict)

A priority queue dictionary maps hashable objects (keys) to priority-determining values. It provides a hybrid dictionary/priority queue API.

Works with Python 2.7+, 3.3+, and PyPy.

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The priority queue is implemented as a binary heap of (key, priority value) pairs, which supports:

  • O(1) search for the item with highest priority
  • O(log n) removal of the item with highest priority
  • O(log n) insertion of a new item

Additionally, an index maps elements to their location in the heap and is kept up to date as the heap is manipulated. As a result, pqdict also supports:

  • O(1) lookup of any item by key
  • O(log n) removal of any item
  • O(log n) updating of any item's priority level


Documentation is available at


This module is released under the MIT license. The augmented heap implementation was adapted from the heapq module in the Python standard library, which was written by Kevin O'Connor and augmented by Tim Peters and Raymond Hettinger.