An ordered dictionary for the Python library?

[Michele Simionato]

On Sep 12, 3:54 pm, Mark Summerfield <m.n.summerfi... at googlemail.com>
wrote:
> On 12 Sep, 13:46, Michele Simionato <michele.simion... at gmail.com>
>
> Actually I meant by key order, so insertion order doesn't matter at
> all. If you need a dictionary-like data structure that respects
> insertion order you could use a list of (key, value) tuples.
>
> Another respondent asked about use cases.
>
> I have found time and again that I needed (key, value) pairs where the
> key is some string that provides a representation for human readers
> and the value is some internal key (e.g., database ID) that the system
> uses internally. In these cases I often need to present the user with
> a list of items from which to choose and want to present them in
> sorted order. Naturally, I could use an ordinary dict and then do
> this:
>
> for string in sorted(d.keys()):
>     process(string)
>
> But what happens when I need to do this a *lot* and when the number of
> items is hundreds or a few thousands? I'm having to sort again and
> again, since it is often the case that the items in the list changes
> during the runtime of the application. So my solution in C++ is to use
> an ordered dictionary (a map in C++ jargon), which in Python means I
> can simply write:
>
> for string in od.keys():
>     process(string)
>

For your use case I would wrap a list [(key, value)] with a dict-like
object and I would use the bisect module in the standard library to
keep
the inner list ordered.

 M.S.