[Python-Dev] Re: opcode performance measurements (original) (raw)

Jeremy Hylton jeremy@alum.mit.edu
Thu, 31 Jan 2002 06:12:26 -0500

"SP" == Samuele Pedroni <pedronis@bluewin.ch> writes:

SP> Hi. Q about PEP 267 Does the PEP mechanims adress only SP> import a SP> use a.x

SP> cases. How does it handle things like SP> import a.b SP> use a.b.x

You're a smart guy, can you tell me? :-). Seriously, I haven't gotten that far.

import mod.sub creates a binding for "mod" in the global namespace

The compiler can detect that the import statement is a package import -- and mark "mod.sub" as a candidate for optimization. A use of "mod.sub.attr" in function should be treated just as "mod.attr".

The globals array (dict-list hybrid, technically) has the publicly visible binding for "mod" but also has an internal binding for "mod.sub" and "mod.sub.attr". Every module or submodule attribute in a function gets an internal slot in the globals. The internal slot gets initialized the first time it is used and then shared by all the functions in the module.

So I think this case isn't special enough to need a special case.

Jeremy