Dear Sjoerd, dear all,

My thoughts:
* on one hand it feels natural to simplify calls and keep things simple,
from this perspective +1;
* on the other I can imagine new Django user that gets confused by
inconsistency in code snippets or StackOverflow: you can now filter not
only using filter() or get() methods, from this perspective -1;
* get() already supports field lookups, so count() and exists() would join
it to stand in one row, from this perspective +1;
* if introducing such change, for sure documentation should be very
carefully reviewed and updated to mirror the new preferred way of doing
count and exists queries;
* it would be quite a big change, I think it should be introduced with
preferably MAJOR or at least MINOR version of Django;
* maybe an e-mail encouraging community to update e.g. StackOverflow with
new Django syntaxt sections after the release to avoid confusion for
newcomers would be a good idea?;
* what about first() and delete()? (rest of queryset methods with no
arguments, that doesn't return a queryset); should they also support field
lookups?
* what about reverse() and all()? (rest of queryset methods with no
arguments that return a queryset); should they also support field lookups?

Kind regards,
Maciej Olko

pt., 18 sty 2019 o 22:12 u┼╝ytkownik Sjoerd Job Postmus <sjoerd...@sjec.nl>
napisał:

> Dear all,
>
>
> This is probably a feature that has been proposed before, but I could
> not find a discussion on it, so I proposed it on the tracker, and Tim
> also couldn't find a discussion.
>
> (ticket: https://code.djangoproject.com/ticket/30118 )
>
> I would like to propose being able to write
> `SomeModel.objects.exists(field=value)` over
> `SomeModel.objects.filter(field=value).exists()` (and similar for
> `.count(**kwargs)`.
>
>
> As Tim rightfully commented: "There should be one-- and preferably only
> one --obvious way to do it.".
>
>
> I'm proposing this is a case where the obvious way would eventually be
> more in line with my suggestion instead of what we currently use.
>
>
> Consider the following code example (from
>
> https://github.com/django/django/blob/709a8b861de14204f0e13c9a0fbfd61c11b3565d/tests/auth_tests/test_management.py#L998
> ):
>
>
>              Permission.objects.filter(
>                  content_type__model=opts.model_name,
>                  content_type__app_label=opts.app_label,
>                  codename=codename,
>              ).exists()
>
> There is a weird (to me, your mileage might vary) ").exists()" as a
> final line, and I would like to write this as
>
>              Permission.objects.exists(
>                  content_type__model=opts.model_name,
>                  content_type__app_label=opts.app_label,
>                  codename=codename,
>              )
>
> This pattern seems to be quite rare in the Django codebase itself, but
> in the codebase at work we have several cases of `queryset.filter(<lots
> of lines>).exists()` (and similar with count), and I am expecting this
> to also be prevalent in other codebases out there.
>
>
> Arguing against it however are the following lines of the Zen of Python:
>
> - "Explicit is better than implicit."
>
> - Maybe also "Special cases aren't special enough to break the rules.",
> because `.filter().count()` and `.exclude().count()` are both the same
> pattern, but this would only create an alternative for the first.
>
> - "There should be one-- and preferably only one --obvious way to do it."
>
>
> Beyond these short quips, I was hoping there might also be an earlier
> discussion covering this.
>
>
> Kind regards,
>
> Sjoerd Job Postmus
>
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