Something annoying about method __set_name__ in descriptors

[ast]

Le 21/04/2020 à 18:32, Dieter Maurer a écrit :
> ast wrote at 2020-4-21 14:27 +0200:

> 
> I recently read the Python (3.9a5) documentation - and there
> I found clearly expressed this behaviour (I no longer can
> tell you exactly where I read this).
> 
> The reason comes from the implementation: when the descriptor
> is instantiated, the name the instance is bound to is not yet known.
> Class creation is complex in Python (details in the Python documentation):
> first a so called "namespace" (a mapping from names to values) is constructed;
> after this construction, the so called metaclass is called with
> class name, bases, the constructed namespace and potentially additional
> keyword arguments. It is the typical metaclass (`type`) which calls
> `__set_name__` for descritors it finds in the namespace.
> 
> This has several ramifications:
> 
>   * `__set_name__` is not called "inline" (as you observed)
> 
>   * `__set_name__` is not called automatically for descriptors added
>     after class construction
> 
>   * `__set_name_` may not be called at all if the class uses
>     a custom metaclass.
> 

Thank you for this explanation.
So it's not a bug it's a feature