[Python-ideas] Augmented assignment syntax for objects.

[Juancarlo Añez]

On Thu, Apr 27, 2017 at 7:28 PM, Steven D'Aprano <steve at pearwood.info>
wrote:

> > In my experience, what Python is lacking is a way to declare attributes
> > outside of the constructor. Take a look at how it's done in C#, Swisft,
> or
> > Go.
>
> Since you apparently already know how they do it, how about telling us
> (1) how they do it, and (2) *why* they do it?
>

They make attribure declarations at the class declaration scope be instance
attributes. Python makes that kind of declaration class attributes (statics
in some other languages).

This is the spec for C#: https://goo.gl/FeBTuy


The reason *why* they do it that way is because declaring instance
fields/variables is much more frequent than declaring class ones.


> > Object attributes outside of the constructor would solve things more
> > relevant than the vertical space used when assigning constructor
> parameters
> > to attributes.
>
> Solve which things?
>

Instance attributes may be defined with or without default values without
having to pass them as arguments to or mention them in a constructor.


> > For example, multiple inheritance is well designed in
> > Python, except that it often requires constructors with no parameters,
> > which leads to objects with no default attributes.
>
> Can you elaborate?


A class hierarchy in which there is multiple inheritance requires
constructors with no arguments. This is typical: https://goo.gl/l54tx7

I don't know which would be the best syntax, but it would be convenient to
be able to declare something like:

class A:

    var a = 'a'


And have "a"  be an instance attribute.

-- 
Juancarlo *Añez*
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