Bruno Desthuilliers wrote:
> Michael Spencer a écrit :
>> I may be missing the subtlety of what you're up to, but why is
>> overriding __getattribute__ more desirable than simply defining the
>> descriptor in a subclass?
>
> The code snippet I gave as an example was not supposed to reflect how I
> effectively mean to use per-instance descriptors, it was just a kind of
> Minimal Working Code (tm). The real life code is about 500 LOC, and
> explaining the whole thing would take far too long. Also, as I said,
> this is mostly syntactic sugar - there are simpler, less 'hackish' (but
> also less elegant) solutions to the actual 'problem'.So, to answer your
> question, no, subclassing would not be a solution - I'd almost need a
> subclass per controller function, which would reintroduce the
> boilerplate I'm trying to get rid of.
>
> BTW, there may be other use case for per-instance descriptors...
Agreed. Per-instance descriptors could be interesting (that's why the subject
line caught my attention).
But your solution involves a custom __getattribute__ in the class, which I
would
always avoid if possible (and I gather you're uneasy about it too).
Here, I don't see why that's better than having a descriptor in the class and,
if it needs per-instance behavior, then make it dependent on something provided
by the instance.
e.g.,
class DummyDescriptor1(object):
def __get__(self, obj, objtype=None):
if isinstance(obj, objtype):
return obj.foo.__get__(obj)
else:
return self
class MyClass4(object):
baaz = DummyDescriptor1()
def __init__(self, foo, bar = None):
self.foo = foo
self.bar = bar
>>> mc4 = MyClass4(lambda self: self.bar, "I'm bar")
>>> mc4.baaz
>>> mc4.baaz()
"I'm bar"
>>> mc5 = MyClass4(lambda self: "I ignore bar", "I'm another bar")
>>> mc5.baaz()
"I ignore bar"
>>>
Python
> is so dynamic that you can almost use it like a prototype-based language.
>
>
Almost, yes.
Michael
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