At 02:28 AM 1/16/2008 +0100, Christian Heimes wrote:
>Phillip J. Eby wrote:
> > At 10:14 PM 1/15/2008 +0100, Christian Heimes wrote:
> >> My code queues up new hooks while a sequence of hooks is processed. It
> >> makes sure that hooks for a parent aren't called in the middle of a
> >> child's hook chain.
> >
> > Notice that that's not necessary with the notification algorithm I gave,
> > since the list in post_import_hooks suffices as a queue. So, just as in
> > peak.util.imports, the registration code doesn't need to know whether
> > callbacks are being run; it only needs to know whether they're *finished*.
>
>Are you sure your proposed algorithm and output match for the test case?
>I'm confident I got it right in C but I'm getting a different output.
I guess it's not right then. ;-) Though I shouldn't make fun, since
it turns out that my code sketch was not a correct translation of
peak.util.imports. (See below.)
>Without the extra imp.notify_module_loaded('a.b') in func_a1(mod)::
>
> ['func_a1', 'func_a2', 'func_ab1', 'func_ab2', 'func_ab3']
>
>
>With the extra imp.notify_module_loaded('a.b') in func_a1(mod)::
>
> ['func_a1', 'func_ab1', 'func_ab2', 'func_ab3', 'func_a2']
Right - that's why I put it in there, to foil trivial implementations
that don't really satisfy the invariant.
>I can't see how your implementation results in the first output when
>func_a1() calls the notification method.
Hm, you're right, my implementation sketch waits too long to set the
__notified__ flag. It should have read:
def notify(name):
try:
module = sys.modules[name]
except KeyError:
raise ImportError("Module %s has not been imported" % (name,))
if module.__notified__:
return
try:
module.__notified__ = True
if '.' in name:
notify(name[:name.rfind('.')])
for callback in post_import_hooks[name]:
callback(module)
finally:
post_import_hooks[name] = None
That is, module.__notified__ has to be set *before* the recursive
notification call. This effectively happens in peak.util.imports
now, except that __notified__ isn't an explicit attribute, just a
side effect of other module state changes.
>I'm aware of the implications and my code already uses the lock. The
>PyImport_NotifyLoaded() method excepts to be called with the importer
>lock acquired. So I'm locking the importer lock in
>imp_notify_module_loaded(). The PyImport_RegisterPostImportHook() method
>does the locking before it accesses sys.modules and sys.post_import_hooks.
Great!
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