+1. I implemented much the same thing for part of django-model-values
<https://pypi.python.org/pypi/django-model-values/>, but went with F
as the basis instead. Primarily because F expressions already support
operator overloading and are a natural intermediate object; from there one
can create Q, OrderBy, and Func objects.
In : from model_values import F
In : F.user.created
In : F.user.created >= 0
Out: <Q: (AND: ('user__created__gte', 0))>
In : F.user.created.min()
In : -F.user.created
Out: OrderBy(FExpr(user__created), descending=True)
In : F.text.iexact('...')
Out: <Q: (AND: ('text__iexact', '...'))>
On Thursday, October 6, 2016 at 10:04:56 AM UTC-7, Alexey Zankevich wrote:
> Hey all,
> Just want to announce recent changes in Django ORM Sugar library, which
> might be useful in future Django query syntax enhancement (if ever happens).
> 1. Now it supports indexes and slices:
> >>> Q.data.owner.other_pets.name='Fishy'
> >>> Q.tags == 'thoughts'
> >>> Q.tags[0:2].contains(['thoughts'])
> 2. Previously, it was only possible to call defined method (like it is
> done for *is_not_null()* function) or registered with decorator. Now if
> you try to call unknown function of sugar Q, it will internally pass
> function name and append it as *__functionname *to lookup field:
> >>> Q.user.username.contains('Rodriguez')
> There is no such function "contains" anymore in sugar Q, however, it just
> adds *__contains* to lookup field and passes parameter to it.
> 3. It will pass a tuple to lookup if multiple arguments passed:
> >>> Q.user.create_datetime.range(d1, d2)
> Q(user__create_datetime__range=(d1, d2))
> I think the library is at the final state now and isn't going to get new
> substantial features, but responses are highly appreciated.
> On Sunday, August 16, 2015 at 4:18:26 PM UTC+3, Alexey Zankevich wrote:
>> Hi all,
>> This topic is related to the current ORM query syntax with underscores.
>> There are lots of arguing related to it, anyway it has pros and cons.
>> Let's take a concrete example of querying a model:
>> 1. The syntax is easy to understand
>> 2. Can be extended with custom transforms and lookups
>> However, there are several cons:
>> 1. Long strings is hard to read, especially if we have fields with
>> It's really easy to make a mistake by missing one:
>> Not easy to catch missing underscore between user and profile, is it? Even
>> though, it's not easy to say whether it should be "user_profile"
>> attribute or
>> user.profile foreign key.
>> 2. Query strings can't be reused, thus the approach violates DRY
>> For example, we need to order results by last_login_date:
>> GameSession.objects.filter(user__profile__last_login_date__gte=yesterday) \
>> We can't keep user__profile_login_date as a variable as in the first part
>> of the
>> expression we use a keyword argument, meanwhile in the second part - just
>> string. And thus we just have to type query path twice.
>> 3. Lookup names not natural to Python language and require to be
>> remembered or
>> looked up in documentation. For example, "__gte" or "__lte" lookups tend
>> to be
>> confused with "ge" and "le" due to similarity to methods "__ge__" and
>> 4. Lookup keywords limited to a single argument only, very inconvenient
>> necessary to filter objects by range.
>> I was thinking a lot trying to solve those issues, keeping in mind Django
>> approaches. Finally I came up with solution to extend Q objects with dot
>> expression syntax:
>> >>> GameSession.objecs.filter(Q.user.profile.last_login_date >= yesterday)
>> Q is a factory instance for old-style Q objects. Accessing attribute by
>> returns a child factory, calling factory will instantiate old-style Q
>> >>> Q
>> <QFactory object at 0x7f407298ee10>
>> >>> Q.user.profile
>> <QFactory object at 0x7f40765da310>
>> >>> Q(user__name='Bob')
>> <Q: (AND: ('user__name', 'Bob'))>
>> It overrides operators, so comparing factory with value returns a related
>> >>> Q.user.name == 'Bob'
>> <Q: (AND: ('user__name', 'Bob'))>
>> Factory has several helper functions for lookups which aren't related to
>> Python operators directly:
>> >>> Q.user.name.icontains('Bob')
>> <Q: (AND: ('user__name__icontains', 'Bob'))>
>> And helper to get query path as string, which requred by order_by or
>> select_related queryset methods:
>> >>> Q.user.profile.last_login_date.get_path()
>> You can check implementation and more examples here
>> How it solves issues:
>> #1. Dots hard to confuse with underscores
>> #2. Query paths can be reused:
>> >>> factory = Q.user.profile.last_login_date
>> >>> query = GameSession.objects.filter(factory >= yesterday)
>> >>> query = query.order_by(factory.get_path())
>> #3. Not neccessary to remember most of lookup names and use comparison
>> #4. Possible to use multiple keyword arguments:
>> >>> Q.user.profile.last_login_date.in_range(from_date, to_date)
>> <Q: (AND: ('user__profile__last_login_date__lte', from_date),
>> ('user__profile__last_login_date__gte', to_date))>
>> This approach looked the best for me due to several reasons:
>> 1. It's explicit - it doesn't do anything but generating appropriate Q
>> The result of comparison can be saved as Q object variable.
>> 2. It's short - variants with using model for that will look much longer,
>> joining two or more filters:
>> >>> GameSession.objects.user.profile_last_login_date >= yesterday #
>> 3. Implementation will not require to change querset manager or model
>> 4. Will still allow to use filters and Q class in the old way:
>> >>> q = Q(user__profile__last_login_date__gte=yesterday)
>> I'd like to make it as a part of Django ORM syntax and it will not be
>> hard to
>> do, especially taking into account the library is already done and
>> Anyway, I need your thought about the idea in general, as well as about
>> particular things like chosen method names - "get_path", "in_range" and
>> As next step I can create a ticket in the issue tracker, or prepare DEP
>> In latter case I need to find a shepherd to work with.
>> Best regards,
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