Alexander Belopolsky <belopol...@users.sourceforge.net> added the comment:
On Thu, Jul 15, 2010 at 8:26 PM, mike bayer <rep...@bugs.python.org> wrote: .. > where is it defined that sets are not "supposed" to contain mutable items? > such a requirement vastly limits the usefulness of sets. > Well, there is no such requirement. The actual requirement is that they should be hashable. For built-in types, however hashable is the same as immutable. Arguably, user-defined classes should emulate that. > Consider that relational database rows are mutable. A result set containing > multiple rows which each have a primary key comprises a set, hashed on > primary key. But other attributes of each row can be updated. Surely this > is not controversial ? What Python data structure should I (and a whole > bunch of Python ORMs) be using to represent mutable, relational database > rows, unordered and unique on primary key, in memory ? Why wouldn't you represent a result set as a dict mapping primary key (tuple) to list of column values? ---------- _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue9269> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
