[Python-Dev] Third and hopefully final post: PEP 557, Data Classes

[Wes Turner]

Sorry, this one shouldn't be "an"; " a" was correct::

  ``repr``: If true (the default), an ``__repr__`` method will be generated.

Note that __repr__ can be dangerous with user-supplied input because of
terminal control character injection (e.g. broken syntax highlighting, \r,
character set, LEDs,)

On Thursday, November 30, 2017, Wes Turner <wes.turner at gmail.com> wrote:

> Could these be things in types?
>
> types.ClassType
> types.InstanceType
>
> types.DataClass
> types.DataClassInstanceType (?)
>
> I sent a PR with typo fixes and ``.. code:: python`` directives so that
> syntax highlighting works (at least on GitHub).
>
> https://github.com/python/peps/blob/master/pep-0557.rst
>
> https://github.com/python/peps/pull/488
>
> Additional notes:
>
> - "DataClass" instead of "Data Class" would be easier to search for.
> s/DataClass/Data Class/g?
> - It's probably worth mentioning how hash works when frozen=True also here:
>   https://github.com/python/peps/blob/master/pep-0557.rst#frozen-instances
> - The `hash` explanation could be a two column table for easier readability
>
> What a great feature.
>
> - Runtime data validation from annotations (like PyContracts,) would be
> cool
> - __slots__ are worth the time
>
> On Thursday, November 30, 2017, Antoine Pitrou <solipsis at pitrou.net
> <javascript:_e(%7B%7D,'cvml','solipsis at pitrou.net');>> wrote:
>
>>
>> isdataclass() testing for instance-ship does sound like a bug magnet to
>> me.
>>
>> If isdataclassinstance() is too long (that's understandable), how about
>> isdatainstance()?
>>
>> Regards
>>
>> Antoine.
>>
>>
>> On Wed, 29 Nov 2017 17:02:21 -0800
>> Guido van Rossum <guido at python.org> wrote:
>> >  On Wed, Nov 29, 2017 at 3:51 PM, Carl Meyer <carl at oddbird.net> wrote:
>> >
>> > > On 11/29/2017 03:26 PM, Eric V. Smith wrote:
>> > > > I've posted a new version of PEP 557, it should soon be available at
>> > > > https://www.python.org/dev/peps/pep-0557/.
>> > > >
>> > > > The only significant changes since the last version are:
>> > > >
>> > > > - changing the "compare" parameter to be "order", since that more
>> > > > accurately reflects what it does.
>> > > > - Having the combination of "eq=False" and "order=True" raise an
>> > > > exception instead of silently changing eq to True.
>> > > >
>> > > > There were no other issues raised with the previous version of the
>> PEP.
>> > >
>> > > Not quite; I also raised the issue of isdataclass(ADataClass)
>> returning
>> > > False. I still think that's likely to be a cause of bug reports if
>> left
>> > > as-is.
>> > >
>> >
>> > I tried to look up the discussion but didn't find much except that you
>> > flagged this as an issue. To repeat, your concern is that isdataclass()
>> > applies to *instances*, not classes, which is how Eric has designed it,
>> but
>> > you worry that either through the name or just because people don't read
>> > the docs it will be confusing. What do you suppose we do? I think
>> making it
>> > work for classes as well as for instances would cause another category
>> of
>> > bugs (confusion between cases where a class is needed vs. an instance
>> > abound in other situations -- we don't want to add to that). Maybe it
>> > should raise TypeError when passed a class (unless its metaclass is a
>> > dataclass)? Maybe it should be renamed to isdataclassinstance()? That's
>> a
>> > mouthful, but I don't know how common the need to call this is, and
>> people
>> > who call it a lot can define their own shorter alias.
>> >
>>
>>
>>
>> _______________________________________________
>> Python-Dev mailing list
>> Python-Dev at python.org
>> https://mail.python.org/mailman/listinfo/python-dev
>> Unsubscribe: https://mail.python.org/mailman/options/python-dev/wes.
>> turner%40gmail.com
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/python-dev/attachments/20171130/6f7c581d/attachment.html>