> From: Michele Simionato > > On Sep 12, 3:54 pm, Mark Summerfield <[EMAIL PROTECTED]> > wrote: > > On 12 Sep, 13:46, Michele Simionato <[EMAIL PROTECTED]> > > > > 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.
Or subclass dict to carry along a sorted list of keys with it and return that when dict.keys() is called. Even better, only have .keys() sort the keys list when a key has been added to it since the last call. -- -Bill Hamilton -- http://mail.python.org/mailman/listinfo/python-list
