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
--
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