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Fallback for operator and other dunder methods

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From: dom.grig...@gmail.com (Dom Grigonis)
Newsgroups: comp.lang.python
Subject: Fallback for operator and other dunder methods
Date: Wed, 26 Jul 2023 05:22:18 +0300
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by: Dom Grigonis - Wed, 26 Jul 2023 02:22 UTC

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

Re: Fallback for operator and other dunder methods

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From: ram...@zedat.fu-berlin.de (Stefan Ram)
Newsgroups: comp.lang.python
Subject: Re: Fallback for operator and other dunder methods
Date: 27 Jul 2023 09:31:36 GMT
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by: Stefan Ram - Thu, 27 Jul 2023 09:31 UTC

Dom Grigonis <dom.grigonis@gmail.com> writes:
>Is there a way to achieve it without actually implementing operators?

main.py

import pydoc_data.topics
import re

numeric_types = pydoc_data.topics.topics[ 'numeric-types' ]
dic = {}
for numeric_operation in re.finditer\
( '^object.(__.*?__)', numeric_types, re.MULTILINE ):
name = numeric_operation.group( 1 )
exec( rf'''def %s( self, /, *args, **kwargs ):
return \
self.implementation( %r, args, kwargs )''' %( name, name ), dic )
base_class = type( name, (object,), dic )

class example_class( base_class ):
def implementation( self, name, *args, **kwargs ):
print( f'implementation called. {name = }' )
return 2

example_object = example_class()

print( example_object + 1 )
print( 1 + example_object )

output

implementation called. name = '__add__'
2 implementation called. name = '__radd__'
2

Re: Fallback for operator and other dunder methods

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From: ram...@zedat.fu-berlin.de (Stefan Ram)
Newsgroups: comp.lang.python
Subject: Re: Fallback for operator and other dunder methods
Date: 27 Jul 2023 09:44:52 GMT
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by: Stefan Ram - Thu, 27 Jul 2023 09:44 UTC

I am NOMAD!

devel / comp.lang.python / Fallback for operator and other dunder methods

Subject	Author
Fallback for operator and other dunder methods	Dom Grigonis
Re: Fallback for operator and other dunder methods	Stefan Ram
Re: Fallback for operator and other dunder methods	Stefan Ram