On Thu, Jan 31, 2013 at 10:28 AM, Chris Angelico <ros...@gmail.com> wrote:
>
> >> Well, that surely isn't going to work, because it always decorates the
> >> same function, the global "fcn".
> >
> >
> > I don't think this is right. fcn is a passed function (at least if it
> acts
> > as a decorator) that is declared locally in the _protector_decorator
> scope.
> > Since newfcn is bound in the same scope and fcn is not defined inside
> > newfcn, I'm pretty sure that newfcn will just grab the fcn passed into
> the
> > decorator.
>
> Yet it adds a level of indirection that achieves nothing. Why not simply:
> def _protector_decorator(fcn):
> return fcn
>
> ? I'm not understanding the purpose here.
>
Bad example. A better (longer) one that is closer to my true use-case:
from somewhere.exceptions import MyTypeError
from somewhere.different import AuthorClass, RemoteAuthorClass
from urllib2 import HTTPError
class A(object):
authorclass = AuthorClass
def __init__(self, obj_list):
"""
Instantiate a list of obj_list objects that may have an "author"
attribute
"""
self.things = []
for o in obj_list:
if not isinstance(o, self.authorclass):
raise MyTypeError('Bad type given to constructor')
self.things.append(o)
def _protector(fcn):
def newfcn(self, *args, **kwargs):
try:
return fcn(self, *args, **kwargs) # returns a string
except AttributeError:
return 'Attribute not available.'
except IndexError:
return 'Not that many AuthorClasses loaded'
return newfcn
@_protector
def author(self, idx):
return self.things[idx].author
@_protector
def description(self, idx):
return self.things[idx].description
@_protector
def hobbies(self, idx):
return self.things[idx].hobbies
class B(A):
authorclass = RemoteAuthorClass
def _protector(fcn):
def newfcn(self, *args, **kwargs):
try:
return fcn(self, *args, **kwargs)
except AttributeError:
return 'Attribute not available'
except IndexError:
return 'Not that many RemoteAuthorClasses loaded'
except HTTPError:
return 'Could not connect'
return fcn
Basically, while RemoteAuthorClass and AuthorClass are related (via
inheritance), the RemoteAuthorClass has the potential for HTTPError's now.
I could just expand the A class decorator to catch the HTTPError, but
since that should not be possible in AuthorClass, I'd rather not risk
masking a bug. I'm under no impressions that the above code will decorate
A-inherited functions with the B-decorator (I know it won't), but that's
the effect I'm trying to achieve...
Thanks!
Jason
--
Jason M. Swails
Quantum Theory Project,
University of Florida
Ph.D. Candidate
352-392-4032
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