On 05/30/10 20:35, Masklinn wrote:
On 2010-05-30, at 11:07 , Lie Ryan wrote:
An advantage of formalizing this in collections would be to enable other Python implementations like PyPy, where id() is expensive, to provide an optimized identitydict.
that their id() is expensive is implementation details, and the developer of PyPy should solve that instead of adding a clutch to the stdlib.
Actually, I'd say the exact opposite: CPython's identity being cheap is an implementation detail, not the other way around, and that is what shouldn't be relied on. In that light, a special-purpose identity dictionary independent from implementation-specific and artificially low id() computation costs is a pretty good idea.
the performance of any Python statement/function is implementation detail. Whether any statement/function is fast or cheap shouldn't be relied on. IMHO, adding a brand new collection module just because a Python implementation has a fast/cheap operations isn't a good reason.