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devel / comp.lang.python / Re: extend behaviour of assignment operator

Re: extend behaviour of assignment operator

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From: dieter@handshake.de (Dieter Maurer)
Newsgroups: comp.lang.python
Subject: Re: extend behaviour of assignment operator
Date: Wed, 10 Jan 2024 19:44:31 +0100
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by: Dieter Maurer - Wed, 10 Jan 2024 18:44 UTC

Guenther Sohler wrote at 2024-1-9 08:14 +0100:
>when i run this code
>
>a = cube([10,1,1])
>b = a
>
>i'd like to extend the behaviour of the assignment operator
>a shall not only contain the cube, but the cube shall also know which
>variable name it
>was assigned to, lately. I'd like to use that for improved user interaction.

`Acquisition` (--> `PyPI`) implements something similar.

It does not work for variables -- but for attribute access.
Look at the following code:

```
from Acquisition import Implicit

class AccessAwareContainer(Implicit):
...

class AccessAwareContent(Implicit):
...

container = AccessAwareContainer()
container.content = AccessAwareContent()
```

When you now assign `content = container.content`, then
`content` knows that it has been accessed via `container`.

If fact `content` is not a true `AccessAwareContent` instance
but a wrapper proxy for it. It mostly behaves like an
`AccessAwareContent` object but has additional information
(e.g. it knows the access parent).

It works via a special `__getattribute__` method, essentially
implemented by:

```
def __getattribute__(self, k):
v = super().__getattribute__(k)
return v.__of__(self) if hasattr(v, "__of__") else v
```

Your use case could be implemented similarly (again not for variables
and all objects, but for special classes (and maybe special objects)).

Your `__getattribute__` could look like:
```
def __getattribute__(self, k):
v = super().__getattribute__(k)
try:
v.name = k
except TypeError: pass
return v
```

Subject	Author
extend behaviour of assignment operator	Dieter Maurer

19 May, 2024: Line wrapping has been changed to be more consistent with Usenet standards. If you find that it is broken please let me know here rocksolid.nodes.help

devel / comp.lang.python / Re: extend behaviour of assignment operator

devel / comp.lang.python / Re: extend behaviour of assignment operator

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