On Fri, 26 Jun 2020 at 14:30, Hans Ginzel <hans@matfyz.cz> wrote:
Date: Fri, 26 Jun 2020 18:47:44 +0200 From: Hans Ginzel <hans@matfyz.cz> To: Hans Ginzel <hans@artax.karlin.mff.cuni.cz> Subject: Access (ordered) dict by index; insert slice
Hello,
thank you for making dict ordered. Is it planned to access key,value pair(s) by index? See https://stackoverflow.com/a/44687752/2556118 for example. Both for reading and (re)writing? Is it planned to insert pair(s) on exact index? Or generally to slice? See splice() in Perl, https://perldoc.perl.org/functions/splice.html.
Use case: Represent database table metadata (columns). It is useful as to access columns both by name and by index as to insert column on specific position, https://dev.mysql.com/doc/refman/8.0/en/alter-table.html, “ALTER TABLE ADD COLUMN [FIRST |AFTER col]” (consider default order or table storage size optimisation by aligning).
These are odd requirements. No - Python dictionaries are ordered, by order of insertion only, but one can't generally do any manipulation by the numeric index of a dictionary entry - and it will stay that way. If you need such an hybrid data structure, you could just have a list of tuples as data structure, and use collections.abc.MutableMapping to provide a dict-like interface to it (and even a parallel dictionary to be used as an index for better than linear search). I could create such a data structure if you want, but I don't see that as useful enough to be part of the language. The part allowing slice-assignment seems, actually, quite confusion prone - since in dictionaries the order is order of insertion, not alphabetical order or any other.
Thank you in advance, Hans PS1: Named tuples cannot be used, are immutable. PS2: See https://metacpan.org/pod/perlref#Pseudo-hashes:-Using-an-array-as-a-hash _______________________________________________ Python-ideas mailing list -- python-ideas@python.org To unsubscribe send an email to python-ideas-leave@python.org https://mail.python.org/mailman3/lists/python-ideas.python.org/ Message archived at https://mail.python.org/archives/list/python-ideas@python.org/message/S7UMTW... Code of Conduct: http://python.org/psf/codeofconduct/