conceiling function calls..
Hung Jung Lu
hungjunglu at yahoo.com
Fri Nov 14 21:38:02 CET 2003
Alex Martelli <aleax at aleax.it> wrote in message news:<gq4tb.20498$9_.728759 at news1.tin.it>...
> You want to HIDE (shudder) the fact that a function is being called,
> ensuring, instead, that just coding:
> print f.someattr
> will call f secretly, behind the scenes.
> If one was truly intent on perpetrating this horror, then:
> class DontLetKidsSeeThisPlease(object):
> def __init__(self, f): self.__f = f
> def __getattr__(self, name): return getattr(self.__f(), name)
> f = DontLetKidsSeeThisPlease(f)
I think the original poster was not very clear in his writing. But he
did give an analogy. Let me try to guess what he wants.
For a property implemented with getter and setter accessor methods,
you can do a lot of things when the user accesses the property. A few
examples are: (a) dynamically retrieve/store the value from/to a
database, (b) do some logging or access security control, (c) return
different values depending on environmental circumstances, etc.
The original poster seems to want the same level of control for access
to a global object inside a module. That's all. That is, he probably
would like to: (a) dynamically assemble the object on the flight,
perhaps from a database, perhaps some meta-programming, notice that a
simple Python namespace entry CANNOT do this trick, because it always
points to the same object. Sure, one way out in Python is to make a
wrapper, but that's exactly what the original poster's "f" is about,
(b) do some logging or security control everytime the object is
accessed, (c) return different objects depending on environmental
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