On 2012-06-20, at 4:30 AM, Steven D'Aprano wrote:
> On Tue, Jun 19, 2012 at 08:11:26PM -0400, Yury Selivanov wrote:
>
>> So using the signature will be OK for 'Foo.bar' and 'Foo().bar', but
>> not for 'Foo.__dict__['bar']' - which I think is fine (since
>> staticmethod & classmethod instances are not callable)
>
> There has been some talk on Python-ideas about making staticmethod and
> classmethod instances callable.
>
> Speaking of non-instance method descriptors, please excuse this silly
> question, I haven't quite understood the implementation well enough to
> answer this question myself. Is there anything needed to make
> signature() work correctly with custom method-like descriptors such as
> this?
>
> http://code.activestate.com/recipes/577030-dualmethod-descriptor
Well, as Nick said -- the PEP way is to create a new Signature with
a first parameter skipped.
But in this particular case you can rewrite it (I'd say preferred way):
class dualmethod:
def __init__(self, func):
self.func = func
def __get__(self, instance, owner):
if instance is None:
return types.MethodType(self.func, owner)
else:
return types.MethodType(self.func, instance)
Or another way, using functools.partial:
class dualmethod:
def __init__(self, func):
self.func = func
def __get__(self, instance, owner):
if instance is None:
return functools.partial(self.func, owner)
else:
return functools.partial(self.func, instance)
Since 'MethodType' and 'partial' are supported by signature(),
everything will work automatically (i.e. first argument will be
skipped)
-
Yury
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