[Python-Dev] New and Improved Import Hooks

[Just van Rossum]

[Guido]
> > I'd be disappointed if adding zipfiles to sys.path wasn't possible.
> > After all that's what PEP 273 says.

[Samuele Pedroni]
> but - if I understand correctly - given the approach taken by the
> import_hooks patch there's the issue:
> 
> consider all directories then all zipfiles

(or vice versa ;-)

> versus consider both kind of import sources according to the order in
> sys.path, which is the most natural extension.

Right. I admit I dismissed sys.path a wee bit too quickly when proposing an
alternative zipimport mechanism.

Regarding sys.import_hooks, I see three possibilities:

#1
    for p in sys.path:
        for hook in sys.import_hooks:
            hook(p, ...)

#2
    for hook in sys.import_hooks:
        for p in sys.path:
            hook(p, ...)

#3
    for hook in sys.import_hooks:
        # the hook can traversing sys.path if needed.
        hook(...)

My current sys.import_hooks patch implements #3 and I think that's the most
logical thing to do; after all sys.path may not be meaningful for a hook. #2
makes little sense I guess. #1 could be an option, but, given the current state
of import.c, would be a lot harder to implement. I also think that #3 is the
most efficient scheme, as the hook can save some local state while traversing
sys.path.

I will change my zipimport hook (which _still_ isn't finished ;-) to also
traverse sys.path, and check for *.zip path endings.

Just