Kirk Strauser schrieb:
> I'm trying to write a decorator that would do something like:
>
> def trace(before, after):
> def middle(func):
> def inner(*args, **kwargs):
> func.im_self.debugfunction(before)
> result = func(*args, **kwargs)
> func.im_self.debugfunction(after)
> return result
> return inner
> return middle
>
> class Foo(object):
> def __init__(self, myname):
> self.name = myname
>
> def debugfunction(self, message):
> print 'Instance %s says: %s' % (self.name, message)
>
> @trace('calling', 'finished')
> def bar(self, arg):
> print arg
>
>>>> Foo('snake').bar(123)
> Instance snake says: calling
> 123
> Instance snake says: finished
>
> The gotcha seems to be that there's no way to get to 'self' from within the
> "inner" function, since func will only have the "normal" attributes:
>
>>>> print dir(func)
> ['__call__', '__class__', '__delattr__', '__dict__', '__doc__', '__get__', '__getattribute__', '__hash__', '__init__', '__module__', '__name__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__str__', 'func_closure', 'func_code', 'func_defaults', 'func_dict', 'func_doc', 'func_globals', 'func_name']
>
> There's no nice im_self to bounce off of or anything. I seem to be going
> about this all wrong. What's a good approach to get the desired effect?
Of course you can get the self - just use the first paramter, because it
*is* self. Self is just a parameter - nothing special.
Alternatively, declare inner like this:
def inner(self, *args, **kwargs):
...
try:
return func(self, *args, **kwargs)
finally:
....
Note the additional try/finally. It's got nothing todo with your
original problem - but you should use it to guarantee that your trace
gets called when leaving the call.
Diez