>> That's not true. Currently, the hasattr() call would report that cb is
>> available, when it is actually not implemented. It would be possible to
>> do something like
>>
>> if hasattr(c, 'cb') and not is_pure(c.cb):
>> c.cb("Hello", "World")
>>
>> is_pure could, for example, look at a function attribute of the
>> callback. You'd write something like
>>
>> @pure_virtual
>> def cb(self, param1, param2):
>> not_implemented
>>
>> Regards,
>> Martin
>
> Hello Martine,
>
> Can you elaborate more on how to use the mechanism you described?
There are various ways to do it; the one I had in mind uses function
attributes:
def pure_virtual(func):
func.pure_virtual = True # only presence of attribute matters,
# not value
return func
def is_pure(method): # method might be either a method or a function
try:
func = method.im_func
except AttributeError:
func = method
return hasattr(func, 'pure_virtual')
not_implemented = object() # could also write pass instead, or raise
HTH,
Martin
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