On Wed, Feb 18, 2009 at 7:51 PM, Emile van Sebille <em...@fenx.com> wrote:
>>>> class open(open):
> ... def mything(self):
> ... print "it's my thing"
Hmm. I guess this is Python 3? In 2.6, open is a function and trying
to subclass it gives an error:
In [10]: open
Out[10]: <built-in function open>
In [11]: class myopen(open): pass
....:
TypeError: Error when calling the metaclass bases
cannot create 'builtin_function_or_method' instances
In any event, it's pretty easy to define a generic delegate in Python
using the __getattr__() hook to delegate attribute access. Here is an
example (that assumes all attributes are methods and doesn't actually
do anything other than delegate):
http://code.activestate.com/recipes/252151/
Here is an example using old-style classes that logs attribute access,
both fields and methods:
class LoggingWrapper:
def __init__(self, instance):
self.__dict__['_instance'] = instance # Actual instance
def __getattr__(self, attrName):
''' Log member access '''
# Get the attribute from the delegate
attrValue = getattr(self._instance, attrName)
# Don't log access to private attributes
if attrName.startswith('_'):
return attrValue
if callable(attrValue):
# Create a delegate function that will log the actual parameters
def delegate(*args, **kwds):
params = []
if args:
params.extend(map(repr, args))
if kwds:
params.extend( ['%s=%s' % (key, repr(value)) for
key, value in kwds.items()] )
paramStr = ', '.join(params)
__log.debug('%s(%s)' % (attrName, paramStr))
return attrValue(*args, **kwds)
return delegate
else:
__log.debug(attrName)
return attrValue
def __setattr__(self, attr, value):
__log.debug('%s = %s' % (attr, repr(value)))
return setattr(self._instance, attr, value)
Kent
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