No trees in the stdlib?

[João Valverde]

Aahz wrote:
> In article <mailman.2139.1245994218.8015.python-list at python.org>,
> Tom Reed  <tomreed05 at gmail.com> wrote:
>   
>> Why no trees in the standard library, if not as a built in? I searched 
>> the archive but couldn't find a relevant discussion. Seems like a 
>> glaring omission considering the batteries included philosophy, 
>> particularly balanced binary search trees. No interest, no good 
>> implementations, something other reason? Seems like a good fit for the 
>> collections module. Can anyone shed some light?
>>     
>
> What do you want such a tree for?  Why are dicts and the bisect module
> inadequate?  Note that there are plenty of different tree implementations
> available from either PyPI or the Cookbook.
>   
A hash table is very different to a BST.  They are both useful. The 
bisect module I'm not familiar with, I'll have to look into that, thanks.

I have found pyavl on the web, it does the job ok, but there no 
implementations for python3 that I know of.

Simple example usage case: Insert string into data structure in sorted 
order if it doesn't exist, else retrieve it.