On Dec 4, 5:48 pm, Steven D'Aprano <[EMAIL PROTECTED]
cybersource.com.au> wrote:
> On Thu, 04 Dec 2008 06:23:28 -0800, k3xji wrote:
> > Hi,
>
> > Is there a way to hook a function call in python? I know __getattr__ is
> > doing for variables,
>
> What do you mean "variables"? Do you mean attributes?
>
> > it is giving us a chance before a field is
> > initialized.
>
> What field? Is a field the same as a variable, or something else?
>
> > Do we have same functionality for methods?
>
> Yes, methods are attributes too, they are reached by the exact same
> mechanism as any other attribute.
>
> Any object with a __call__ method can be called. Normally you create
> objects with a __call__ method by using def or lambda.
>
> > Example:
>
> > class Foo(object):
> > def __call_method__(self, ...) # just pseudo
> > print 'A method is called in object...'
>
> > f = Foo()
> > f.test_method()
>
> > I think you understand my point.
>
> I wish I did. It might have helped if you actually showed the expected
> output of your "test_method", instead of expecting us to *guess* what you
> expect to happen.
>
> I'm going to guess what you mean, and show you one possible solution.
> Read it carefully: it shows three examples of __getattr__, starting from
> the simplest to the relatively complicated.
>
> class Parrot(object):
> def __getattr__(self, name):
> if name == "colour":
> return "red"
> elif name == "talk":
> return lambda x: "Hi, I'm %s the talking parrot" % x
> elif name == "speak":
> class Birdy(object):
> def __init__(self, name):
> self.name = name
> def __call__(self):
> return "I'm the talking Parrot %s" % self.name
> return Birdy('Fred')
> else:
> raise AttributeError
>
> And in use:
>
> >>> p = Parrot()
> >>> p.colour
> 'red'
> >>> p.talk # get the attribute "talk"
>
> <function <lambda> at 0x81fab1c>
>
> >>> p.talk("Fred") # call the attribute (method) "talk"
>
> "Hi, I'm Fred the talking parrot"
>
> >>> p.speak
>
> <__main__.Birdy object at 0x820076c>>>> p.speak()
>
> "I'm the talking Parrot Fred"
>
> --
> Steven
Thank you for all the answers. I have given a bad example but got
great answers. So let me clarify my problem again.
I think "decorator of Bruno" and the "third example of Steven" is what
I am looking for.
Steven you embed a callable object in __getattr__ to accomplish what I
want. But my problem:
My problem is that I have a very-multithreaded application that I want
to profile dynamically. And I want to see how many functions are
called/how much time spent on them.(I tried Profilers but lack of
multithreading support I cannot do what I want to do.)
So, from your answers above, if I use a decorator I will not be able
to understand that the function has finished processing. And if I use
the "callable object" Steven's third solution, I will need to convert
every function I want to profile to a callable object.
I think problem is clarified now. Maybe you have other suggestions?
Thanks,
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