[Python-Dev] PEP 557: Data Classes

Steve Holden steve at holdenweb.com
Sat Sep 16 14:14:02 EDT 2017

​I make this suggestion in trepidation, given that Guido called a halt on
the Great Naming Debate, but it seems that a short, neutral name with data
connotations previously not a part of many popular subsystems is required.

I therefore propose "row", which is sufficiently neutral to avoid most
current opposition and yet a common field-oriented mechanism for accessing
units of retrieved data by name.


Steve Holden

On Sat, Sep 16, 2017 at 3:44 PM, Sven R. Kunze <srkunze at mail.de> wrote:

> 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?
> Cheers,
> Sven
> PS: @Michel good observation 1). Typing decorators in shell is annoying.
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