Question

I need a collection data-structure that can do the following:

• Be sorted
• Allow me to quickly pop values off the front and back of the list O(log n)
• Remain sorted after I insert a new value
• Allow a user-specified comparison function, as I will be storing tuples and want to sort on a particular value
• Thread-safety is not required
• Optionally allow efficient haskey() lookups (I’m happy to maintain a separate hash-table for this though)

My thoughts at this stage are that I need a priority queue and a hash table, although I don’t know if I can quickly pop values off both ends of a priority queue. Another possibility is simply maintaining an OrderedDictionary and doing an insertion sort it every-time I add more data to it.

Because I’m interested in performance for a moderate number of items (I would estimate less than 200,000), I am unsure about what asymptotic performance I require for these operations. n will not grow infinitely, so a low constant performance k in k * O(n) may be as important O(n). That said, I would prefer that both the insert and pop operations take O(log n) time.

Furthermore, are there any particular implementations in Python? I would really like to avoid writing this code myself.

Answer 1

You might get good performance for these kinds of operations using blist or a database (such as the sqlite which is in the stdlib).