On Mon, 19 Jun 2017 06:04:57 +1000, Chris Angelico wrote: > On Mon, Jun 19, 2017 at 5:27 AM, <pavlovevide...@gmail.com> wrote: >> I am thinking of a list that actively maintains in its items a member >> that contains the item's own index in the list. Basically, the item >> knows its index into the list and the list ensures that the index >> remains in sync. If the list is changed, the list updates the indices. >> This is a the that might be useful in implementing observer pattern.
How would you use this? Can you give some demonstration pseudo-code? > With a list? No, I would say it's a bad idea. Why a bad idea? As opposed to "can't be done", or "too hard and slow". > But with a dictionary, you > certainly can. Consider something that loads up something based on its > unique ID (which could be a number or a string or something), and then > the thing itself has that ID. Very common in databasing, for instance. > You can then have a lookup dictionary where you grab them from your > cache, and the objects themselves have a "foo.id" attribute. > The IDs are immutable and eternal, unlike list indices, and they are > truly a feature of the object, so this makes a lot of sense. And it's > something I've done reasonably often. -- Steve -- https://mail.python.org/mailman/listinfo/python-list
