inspect feature

[Bruno Desthuilliers]

Aaron "Castironpi" Brady a écrit :
> On Oct 9, 3:48 am, Bruno Desthuilliers <bruno.
> 42.desthuilli... at websiteburo.invalid> wrote:
>> Aaron "Castironpi" Brady a écrit :
>>
>>
>>
>>> Hello,
>>> The 'inspect' module has this method:
>>> inspect.getargvalues(frame)
>>> It takes a frame and returns the parameters used to call it, including
>>> the locals as defined in the frame, as shown.
>>>>>> def f( a, b, d= None, *c, **e ):
>>> ...     import inspect
>>> ...     return inspect.getargvalues( inspect.currentframe() )
>>> ...
>>>>>> f( 0, 1, 'abc', 'def', ( 3, 2 ), h= 'ghi' )
>>> (['a', 'b', 'd'], 'c', 'e', {'a': 0, 'c': ('def', (3, 2)), 'b': 1,
>>> 'e': {'h': 'g
>>> hi'}, 'd': 'abc', 'inspect': <module 'inspect' from 'C:\Programs
>>> \Python26\lib\in
>>> spect.pyc'>})
>>> However, if you wanted a decorator that examines the parameters to a
>>> function, you're out of luck.  By the time you have a frame, you're
>>> already in the function.
>> Hem...
>>
>> def decorator(func):
>>      def _decorator(*args, *kw):
>>          print "func args are ", *args, **kw
>>          return func(*args, **kw)
>>      return _decorator
> 
> It is less of a problem without tuple unpacking, but you still have
> code like:
> 
> if len( args )>= 2:
>    b= args[ 1 ]
> else:
>    try:
>       b= (somehow check b's default val.)
>    except NoDefaultVal:
>       raise ArgumentError
> 
> Worse yet, you have it for each parameter.  Unless I missed something,
> this is the only way to mimic/recreate the signature of the decoratee.

I don't get what you're after ??? The decorator has full access to both 
the actual params *and* the function's signature (via 
inspect.getargspec). So your initial question "if you wanted a decorator 
that examines the parameters to a function" seems fully answered. You 
will indeed have to write a couple lines of code if you want the same 
formating as the one you'd get with inspect.currentframe(), but what ?

FWIW, Michele Simionato's decorator module has some trick to allow for 
signature-preserving decorators, so you may want to have a look - but 
I'm not sure if this would solve your problem - at least in a sane way.