Re: Fallback for operator and other dunder methods

[Dom Grigonis via Python-list]

The issue was more of a wrapping around numpy array. Found the solution 
already. Unfortunately, there is no equivalent to __getattr__, the only way is 
to dynamically define them from meta. It seems it’s pretty standard to just 
have a collection of special method names and using them for similar cases. 
Well, at least it’s what I got to. __getattr__ feels very hacky for such case, 
so maybe it’s for the best.

> On 2 Aug 2023, at 19:54, Edmondo Giovannozzi via Python-list 
>  wrote:
> 
> Il giorno mercoledì 26 luglio 2023 alle 20:35:53 UTC+2 Dom Grigonis ha 
> scritto:
>> Tried exactly that and didn’t work. Neither __getattr__, nor 
>> __getattribute__ of meta is being invoked.
>>> On 26 Jul 2023, at 10:01, Chris Angelico via Python-list 
>>> http://python.org/>> wrote: 
>>> 
>>> On Wed, 26 Jul 2023 at 16:52, Dom Grigonis >> ...@gmail.com > wrote: 
 
 Could you give an example? Something isn’t working for me. 
 
>>> 
>>> This is a metaclass: 
>>> 
>>> class Meta(type): 
>>> ... 
>>> class Demo(metaclass=Meta): 
>>> ... 
>>> 
>>> In order to catch those kinds of attribute lookups, you'll need the 
>>> metaclass to hook them. And you might need to use __getattribute__ 
>>> rather than __getattr__. However, there may also be some checks that 
>>> simply look for the presence of the attribute (see: slots), so you may 
>>> find that it's even more complicated. It's usually easiest to just 
>>> create the slots you want. 
>>> 
>>> ChrisA
>>> -- 
>>> https://mail.python.org/mailman/listinfo/python-list
> 
> 
> For numpy arrays you can find some suggestion at: 
> https://numpy.org/doc/stable/user/basics.dispatch.html 
> 
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Re: Fallback for operator and other dunder methods

[Edmondo Giovannozzi via Python-list]

Il giorno mercoledì 26 luglio 2023 alle 20:35:53 UTC+2 Dom Grigonis ha scritto:
> Tried exactly that and didn’t work. Neither __getattr__, nor __getattribute__ 
> of meta is being invoked.
> > On 26 Jul 2023, at 10:01, Chris Angelico via Python-list 
> >  wrote: 
> > 
> > On Wed, 26 Jul 2023 at 16:52, Dom Grigonis  wrote: 
> >> 
> >> Could you give an example? Something isn’t working for me. 
> >> 
> > 
> > This is a metaclass: 
> > 
> > class Meta(type): 
> > ... 
> > class Demo(metaclass=Meta): 
> > ... 
> > 
> > In order to catch those kinds of attribute lookups, you'll need the 
> > metaclass to hook them. And you might need to use __getattribute__ 
> > rather than __getattr__. However, there may also be some checks that 
> > simply look for the presence of the attribute (see: slots), so you may 
> > find that it's even more complicated. It's usually easiest to just 
> > create the slots you want. 
> > 
> > ChrisA
> > -- 
> > https://mail.python.org/mailman/listinfo/python-list


For numpy arrays you can find some suggestion at: 
https://numpy.org/doc/stable/user/basics.dispatch.html
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Re: Fallback for operator and other dunder methods

[Dom Grigonis via Python-list]

Tried exactly that and didn’t work. Neither __getattr__, nor __getattribute__ 
of meta is being invoked.

> On 26 Jul 2023, at 10:01, Chris Angelico via Python-list 
>  wrote:
> 
> On Wed, 26 Jul 2023 at 16:52, Dom Grigonis  wrote:
>> 
>> Could you give an example? Something isn’t working for me.
>> 
> 
> This is a metaclass:
> 
> class Meta(type):
>...
> class Demo(metaclass=Meta):
>...
> 
> In order to catch those kinds of attribute lookups, you'll need the
> metaclass to hook them. And you might need to use __getattribute__
> rather than __getattr__. However, there may also be some checks that
> simply look for the presence of the attribute (see: slots), so you may
> find that it's even more complicated. It's usually easiest to just
> create the slots you want.
> 
> ChrisA
> -- 
> https://mail.python.org/mailman/listinfo/python-list

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Re: Fallback for operator and other dunder methods

[Dieter Maurer via Python-list]

Dom Grigonis wrote at 2023-7-26 05:22 +0300:
> ...
>Is there a way to achieve it without actually implementing operators?
>I have looked at Proxy objects, but they do not seem suited to achieve this.

Proxying is a good approach:
you might have a look at `dm.reuse.proxy.OverridingProxy` (--> `dm.reuse`
on PyPI).
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Re: Fallback for operator and other dunder methods

[Chris Angelico via Python-list]

On Wed, 26 Jul 2023 at 16:52, Dom Grigonis  wrote:
>
> Could you give an example? Something isn’t working for me.
>

This is a metaclass:

class Meta(type):
...
class Demo(metaclass=Meta):
...

In order to catch those kinds of attribute lookups, you'll need the
metaclass to hook them. And you might need to use __getattribute__
rather than __getattr__. However, there may also be some checks that
simply look for the presence of the attribute (see: slots), so you may
find that it's even more complicated. It's usually easiest to just
create the slots you want.

ChrisA
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Re: Fallback for operator and other dunder methods

[Dom Grigonis via Python-list]

Could you give an example? Something isn’t working for me.

> On 26 Jul 2023, at 09:40, Chris Angelico via Python-list 
>  wrote:
> 
> On Wed, 26 Jul 2023 at 12:23, Dom Grigonis via Python-list
>  wrote:
>> print(a + 1)# TypeError: unsupported operand type(s) for +: 'A' 
>> and 'int'
>> 
>> Is there a way to achieve it without actually implementing operators?
>> I have looked at Proxy objects, but they do not seem suited to achieve this. 
>> (e.g. wrapt)
> 
> These kinds of special methods are not looked up on the object, but on
> the type. It's more like type(a).__add__(a, 1). So you would need a
> metaclass for this.
> 
> ChrisA
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Re: Fallback for operator and other dunder methods

[Chris Angelico via Python-list]

On Wed, 26 Jul 2023 at 12:23, Dom Grigonis via Python-list
 wrote:
> print(a + 1)# TypeError: unsupported operand type(s) for +: 'A' 
> and 'int'
>
> Is there a way to achieve it without actually implementing operators?
> I have looked at Proxy objects, but they do not seem suited to achieve this. 
> (e.g. wrapt)

These kinds of special methods are not looked up on the object, but on
the type. It's more like type(a).__add__(a, 1). So you would need a
metaclass for this.

ChrisA
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Fallback for operator and other dunder methods

[Dom Grigonis via Python-list]

To illustrate what I was trying to achieve:

class A:
def __init__(self, arr):
self.arr = arr

def __getattr__(self, name):
arr_method = getattr(self.arr, name)
def wrapper(*args, **kwargs):
new_arr = arr_method(*args, **kwargs)
return type(self)(new_arr)
return wrapper

a = A(np.ones((1, 1)))
print(a.sum().arr)  # 1
print(a + 1)# TypeError: unsupported operand type(s) for +: 'A' and 
'int'

Is there a way to achieve it without actually implementing operators?
I have looked at Proxy objects, but they do not seem suited to achieve this. 
(e.g. wrapt)

If there is no way to do this, wouldn’t it be sensible to have a new method, 
say ‘__getattrspecial__’? Either with ability to customise for which operators 
it is being called or not.


—Nothing ever dies, just enters the state of deferred evaluation—
Dg

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