[Python-Dev] Switch statement (original) (raw)

Phillip J. Eby pje at telecommunity.com
Fri Jun 23 20:27:18 CEST 2006

At 07:51 PM 6/23/2006 +0200, M.-A. Lemburg wrote:

Furthermore, the compiler could do other optimizations on the const declared names, such as optimizing away global lookups and turning them into code object constants lookups.

Technically, they'd have to become LOAD_DEREF on cells set up by the module level code and attached to function objects. 'marshal' won't be able to save function references or other such objects to a .pyc file.

It's interesting that this line of thinking does get us closer to the long-desired builtins optimization. I'm envisioning:

 static __builtin__.*

or something like that. Hm. Maybe:

 from __builtin__ import static *

:)

In practice, however, this doesn't work for * imports unless it causes all global-scope names with no statically detectable assignments to become static. That could be a problem for modules that generate symbols dynamically, like 'opcode' in the stdlib.

OTOH, maybe we could just have a LOAD_STATIC opcode that works like LOAD_DEREF but falls back to using globals if the cell is empty.

Interestingly, a side effect of making names static is that they also become private and untouchable from outside the module.

Hm. Did I miss something, or did we just solve builtin lookup optimization? The only problem I see is that currently you can stick a new version of 'len()' into a module from outside it, shadowing the builtin. Under this scheme (of making all read-only names in a module become closure variables), such an assignment would change the globals, but have no effect on the module's behavior, which would be tied to the static definitions created at import time.

-- Marc-Andre Lemburg eGenix.com

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