[Python-Dev] Retrieve an arbitrary element from a set without removing it (original) (raw)

"Martin v. Löwis" martin at v.loewis.de
Sun Oct 25 19:43:52 CET 2009

Given Alexander's premise, I agree with your response. But his premise is wrong. Python's current builtin set class maps abstract equivalence classes to representative members. And this is useful. Mapping arbitrary members of such classes to representative members, sometimes called 'canonical', is a standard problem/goal in math. String interning is an application of this idea.

Right. However, this is conceptually a function. In some cases (like string interning), it is mutable (over time) and finite (at any point in time). We already have a data type that can perfectly represent mutable finite funcitons, namely dictionaries. And indeed, interning is implemented by a dictionary.

What Alexander wants is that the set type also becomes useful for storing canonical representations. I find that inappropriate, since dicts already provide the one obvious way to do it.

Regards, Martin

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