Develop Reference

django-filter chained select

I'm using django-filters lib https://django-filter.readthedocs.io/en/master/index.html. I need to make chained select dropdown in my filters.
I knew how to make it with simple django-forms like here https://simpleisbetterthancomplex.com/tutorial/2018/01/29/how-to-implement-dependent-or-chained-dropdown-list-with-django.html.
When user pick region, i need to show cities in this region? Have someone idea or solution how to build filters like this?

Integrate django-smart-selects with how you perform the filtering.
This package allows you to quickly filter or group “chained” models by adding a custom foreign key or many to many field to your models. This will use an AJAX query to load only the applicable chained objects.
In analogy to the original question for Region -> City, the documentation's example is Continent -> Country which fits exactly to what is needed.
Once you select a continent, if you want only the countries on that continent to be available, you can use a ChainedForeignKey on the Location model:
class Location(models.Model):
continent = models.ForeignKey(Continent)
country = ChainedForeignKey(
Country,
chained_field="continent", # Location.continent
chained_model_field="continent", # Country.continent
show_all=False, # only the filtered results should be shown
auto_choose=True,
sort=True)
Related question:
How to use django-smart-select

Odoo 10 - Counting values of linked records

In Odoo 10 I have created my own custom application (using the new studio feature), however I have run into an issue trying to compute data between records that belong to different views.
In the scenario I have two models (model A and model B), where records from model B are connect to records from model A via a many2one relational field. There is a field in Model B that counts a numerical value entered into it.
Ideally what I would like to achieve is have some form of Automated Action / Server Action, that loops through the records in Model A, then loops through related records in Model B adding together the values of the previously mentioned numerical value field and sets the value of a field in model A equal to the equated number, before continuing onto the next record.
For example sake say the field names are:
Model A = x_a
- Model A ID Field = x_id_field
- Target field for computed value = x_compute
Model B = x_b
- many2one field = x_a_id
- numerical field = x_value_field
I have attempted to use the automated actions to execute some basic Python code (because I thought this would be as simple as a nested loop) however all my attempts have been failures due to not being familiar with how to loop through records in odoo and how to access other models and their records (from python).
How would I go about accomplishing this?

Ideally what I would like to achieve is have some form of Automated
Action / Server Action, that loops through the records in Model A,
then loops through related records in Model B adding together the
values of the previously mentioned numerical value field and sets the
value of a field in model A equal to the equated number, before
continuing onto the next record.
Create an Automated Action with Related Document Model = model a
On the Actions tab create a Server Action:
model_b_records = self.env['model_b'].search([('many2one_field', '!=', False)])
for record in model_b_records:
record.many2one_field.target_field_for_computed_value = record.numerical_field
Save the Server Action and execute it.
The code should be self-explanatory, for any questions do not hesitate to ask and comment below.

save a tuple to a django model

Is there a way to save a tuple to a django model?
example:
Class User(models.Model):
location = models.tupleField()
where User.location = (longitude, latitude)

Maybe you are looking for GeoDjango's PointField:
from django.contrib.gis.db import models
Class User(models.Model):
location = models.PointField(help_text="Represented as (longitude, latitude)”)

Honestly, i didn't see tupleField in django documentation. I think better approach is add two fields
longitude and latitude or create another model to store location and in User model add ForeignKey.

If you feel the need to save tuples in a single field, you should really look into relationships. That's the reason they were created.
Old answer:
This answer is assuming you're really saving locations.
If you're using PostgreSQL, you can use PostGIS. MySQL and Oracle has spacial fields built-in.
Django already supports Geo data. E.g. -
from django.contrib.gis.db import models
class ModelName(models.Model):
centroid = models.GeometryField(blank=True, null=True)
Then you can make all sorts of geo queries(e.g. find places that are within a specified area, sorted by distance etc) and your DBMS will take care of them. Plus from that single field, you can access your data like -
lat, long = [modelobject.centroid.x, modelobject.centroid.y]
# Or you can just use .x or .y directly
You can read more about them in the Geodjango documentation.

I recommend the Django-Geoposition app, and for extra, you can see the Latitude and Longitude in Google Maps.

I think this answer could help here as well.
--
As #p14z suggests, the best way to save my tuple was the ArrayField. For my example, I just wanted to save a Polygon extent, with this format:
(3.7739613717694787, 50.31527681737183, 4.726162032377, 50.49743217278623)
from django.contrib.postgres.fields import ArrayField
my_tuple_field = ArrayField(models.FloatField(), size=4, null=True)

Django adding data to models from another class

I have too models speakerCabinet and speakerElement. speakerCabinet has many-to-many relation to speakerElement.
I need to do some calculations on ideal speaker cabinet size that are using some of the speakerElement variables. I would like to contain these calculations to separate class because they are also used without the model.
Then comes the tricky part. My view gets the speakerCabinet instance and generates the speaker element info with:
{% for cab in speakerCabinet.SpeakerElement.all %}
Is there any simple way add that calculation data to my speaker element model?

Django: calculate average, and sort by field in submodel

I have a Product model, with a one-to-many relation with a Rating model. I was previously storing an average_stars field in Product model, which I would update everytime a new Rating was added for that Product model. I would have a function in views.py which would return a QuerySet of all Product instances, ordered by average_star. Is there a way to do this more dynamically using a combination of .aggregate and .order_by, or anything along these lines.
In other words, is there a way to calculate the average for each product from all its respective Rating models, and sort them by that attribute? And which approach is better?

Assuming that your Rating model has a stars field, then you should use annotate:
from django.db.models import Avg
Product.objects.annotate(average_stars = Avg('rating__stars')).order_by('-average_stars')