[Python-Dev] PEP 557: Data Classes

Sven R. Kunze srkunze at mail.de
Sat Sep 16 10:44:34 EDT 2017

Thanks for the PEP! :)

I like the naming. ;) Though, I would like to add to Michel's argument 
in favor of a base class.

On 11.09.2017 08:38, Michel Desmoulin wrote:
>>> - I read Guido talking about some base class as alternative to the
>>> generator version, but don't see it in the PEP. Is it still considered ?
>> I'm going to put some words in explaining why I don't want to use base
>> classes (I don't think it buys you anything). Do you have a reason for
>> preferring base classes?
> Not preferring, but having it as an alternative. Mainly for 2 reasons:
> 1 - data classes allow one to type in classes very quickly, let's
> harvest the benefit from that.
> Typing a decorator in a shell is much less comfortable than using
> inheritance. Same thing about IDE: all current ones have snippet with
> auto-switch to the class parents on tab.
> All in all, if you are doing exploratory programming, and thus
> disposable code, which data classes are fantastic for, inheritance will
> keep you in the flow.
> 2 - it will help sell the data classes
> I train a lot of people to Python each year. I never have to explain
> classes to people with any kind of programming background. I _always_
> have to explain decorators.
> People are not used to it, and even kind fear it for quite some time.
> Inheritance however, is familiar, and will not only push people to use
> data classes more, but also will let them do less mistakes: they know
> the danger of parent ordering, but not the ones of decorators ordering.

3)  - the order of base classes can arranged appropriately

In our day-to-day work, we use mixins and cooperative multiple 
inheritance a lot.
So, having dataclasses as a base class or a mixin would be great! :)

Combined with 1) and 2), I am much in favor of having dataclasses as 
base class/mixin than as a decorator.
What are the benefits of the decorator? Maybe both is possible?


PS: @Michel good observation 1). Typing decorators in shell is annoying.

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