[Python-ideas] Putting `blist` into collections module

[Guido van Rossum]

So write a PEP for sorted dict and tree.

I rarely seem to need ordereddict myself, but it makes a clean LRU cache.

On Saturday, September 20, 2014, David Wilson <dw+python-ideas at hmmz.org>
wrote:

> On Sun, Sep 21, 2014 at 02:37:39PM +1000, Steven D'Aprano wrote:
>
> > > In 2007, this PEP was created that suggested integrating Daniel
> Stutzbach's
> > > blist into Python: http://legacy.python.org/dev/peps/pep-3128/
> > >
> > > The PEP was rejected, but Raymond Hettinger made a note that "after a
> few
> > > months, I intend to poll comp.lang.python for BList success stories. If
> > > they exist, then I have no problem with inclusion in the collections
> > > module."
> >
> > I have not used blist, but I have no objection to it becoming a
> > collections type if the author agrees.
>
> It seems unsettling that we'd consider adding another special use
> collection to the stdlib, when more widely applicable generalizations of
> it are missing. In blist's case, it can (mostly) be trivially
> reimplemented using an ordered map, which the standard library lacks.
> The remainder of blist (IIRC) are some fancy slicing and merging methods
> that exploit the underlying structure.
>
> Even after reviewing the original PEP, the presence of OrderedDict (and
> particularly under that moniker) feels wrong. Since its addition, in
> every case I've encountered it in commercial code, the use has been
> superfluous, diabolically miscomprehended, or used as a hacky stand-in
> for some cleaner, simpler approach.
>
> Coming from this perspective, I'd prefer that further additions were
> limited to clean and far better understood structures. In this light,
> could we perhaps instead discuss the merits of a collections.Tree,
> collections.SortedDict or similar?
>
>
> > which makes blist an optimization, if and when it is available.
>
> blist has functionality that would require significant boilerplate to
> replicate in normal code, so it's definitely not just useful as an
> optimization.
>
>
> David
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-- 
--Guido van Rossum (on iPad)
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