On Fri, Jan 28, 2011 at 11:32, Alan Franzoni wrote:
> On Thu, Jan 27, 2011 at 11:41 PM, Daniel Urban wrote:
>
>> Actually it can. You don't have to modify the object, just check for
>> the desired methods/signature/whatever. See for example the
>> implementation of collections.Hashable.__subclass
On Thu, Jan 27, 2011 at 11:41 PM, Daniel Urban wrote:
> Actually it can. You don't have to modify the object, just check for
> the desired methods/signature/whatever. See for example the
> implementation of collections.Hashable.__subclasshook__ in _abcoll.py
> and the abc.ABCMeta.__instancecheck_
On Thu, Jan 27, 2011 at 20:05, Alan Franzoni wrote:
> On Thu, Jan 27, 2011 at 8:03 PM, Alan Franzoni wrote:
>> Yes, __instancecheck__ could be used as an alternative hook with
>> respect to maybe_implemented_by(), but there's no such logic for
>> signature checking. That's a minor detail, I think
On Thu, Jan 27, 2011 at 10:30 PM, Carl Banks wrote:
> Write some kind of signature proxy to do it.
I don't have a specific implementation idea yet, I see how that grows.
> Based on this thread, you have quite specific requirements, so it's
> doubtful someone else has implemented exactly what you
On Jan 24, 2:13 am, Alan Franzoni wrote:
> Hello,
> I'd like to have a system which lets me do certain actions if the
> duck-type of a certain objects matches what I expect, i.e. I'd like to
> have a formalization of what it's sometimes done through getattr()
> calls:
>
> if getattr(myobj, "someme
On Thu, Jan 27, 2011 at 8:58 PM, Ethan Furman wrote:
> When you signature check, do you mean counting the number of arguments, or
> actually checking argument types?
In order to check for argument types I should either assume type
annotation (python 3 only, optional) or parse the docstring for th
Alan Franzoni wrote:
Hello,
I'd like to have a system which lets me do certain actions if the
duck-type of a certain objects matches what I expect, i.e. I'd like to
have a formalization of what it's sometimes done through getattr()
calls:
if getattr(myobj, "somemethod", None) is not None:
my
On Thu, Jan 27, 2011 at 8:03 PM, Alan Franzoni wrote:
> Yes, __instancecheck__ could be used as an alternative hook with
> respect to maybe_implemented_by(), but there's no such logic for
> signature checking. That's a minor detail, I think.
On the contrary, now that I double checked, it can't be
On Wed, Jan 26, 2011 at 7:23 PM, Daniel Urban wrote:
>> That's just what I'd like and I suppose can't be currently done with
>> current ABC, PyProtocols or zope.interface implementations, right?
>
> It can. With __instancecheck__ you can override isinstance. It is
> possible (for example) to write
> That's just what I'd like and I suppose can't be currently done with
> current ABC, PyProtocols or zope.interface implementations, right?
It can. With __instancecheck__ you can override isinstance. It is
possible (for example) to write a subclass of abc.ABCMeta, which
extends __instancecheck__ t
On Tue, Jan 25, 2011 at 6:48 PM, Terry Reedy wrote:
> This is correct!
>
> print(len(mo))
> TypeError: object of type 'MyObj' has no len()
That's interesting. I must admit I was not thinking about special
methods in my original post, I used that example just because of Chris
response.
by the way
On 1/25/2011 10:32 AM, Alan Franzoni wrote:
You're right, I forgot about subclass check. But that's really a
placebo, because it statically checks the object's *class* for such
method,
That is exactly the proper check. Instance *methods* are defined on the
class.
> not the actual instance:
On Tue, Jan 25, 2011 at 7:55 AM, Chris Rebert wrote:
> Not true actually:
>
> Python 2.7.1 (r271:86832, Dec 5 2010, 00:12:20)
> [GCC 4.2.1 (Apple Inc. build 5664)] on darwin
> Type "help", "copyright", "credits" or "license" for more information.
class MyContainer(object):# no special inheri
On Mon, Jan 24, 2011 at 2:13 AM, Alan Franzoni wrote:
> Hello,
> I'd like to have a system which lets me do certain actions if the
> duck-type of a certain objects matches what I expect, i.e. I'd like to
> have a formalization of what it's sometimes done through getattr()
> calls:
>
> if getattr(m
Hello,
I'd like to have a system which lets me do certain actions if the
duck-type of a certain objects matches what I expect, i.e. I'd like to
have a formalization of what it's sometimes done through getattr()
calls:
if getattr(myobj, "somemethod", None) is not None:
myobj.somemethod(somevalu
15 matches
Mail list logo
