[Python-Dev] Question about dictobject.c:lookdict_string

[Eyal Lotem]

On 6/11/07, Carl Friedrich Bolz <cfbolz at gmx.de> wrote:
> Eyal Lotem wrote:
> > My question is specifically regarding the transition back from
> > lookdict_string (the initial value) to the general lookdict.
> >
> > Currently, when a string-only dict is trying to look up any
> > non-string, it reverts back to a general lookdict.
> >
> > Wouldn't it be better (especially in the more important case of a
> > string-key-only dict), to revert to the generic lookdict when a
> > non-string is inserted to the dict, rather than when one is being
> > searched?
> [...]
> > This does not seem like a significant issue, but as I know a lot of
> > effort went into optimizing dicts, I was wondering if I am missing
> > something here.
>
> Yes, you are: when doing a lookup with a non-string-key, that key could
> be an instance of a class that has __hash__ and __eq__ implementations
> that make the key compare equal to some string that is in the
> dictionary. So you need to change to lookdict, otherwise that lookup
> might fail.
Ah, thanks for clarification.

But doesn't it make sense to only revert that single lookup, and not
modify the function ptr until the dict contains a non-string?

Eyal