We Keep Coding

How do I create two sign-up systems?

So I wanted to create 2 signup options on the website. For example a student and teacher login methods. I want the form or model to extend and save it to the sqlite3 db. For example, if a student signs up the database would store a field isteacher = False and vise versa.
Also once they login is there a way to display two different dashboards based on the user?
Is there any guide or link to show me how to build this step by step? I have spent close to 8 hours figuring this out and i'm very close to giving up. Thanks for your time.

You don't need two sign up forms for such a thing if the students and teachers use the same credentials (e.g. username/email and password). Just simply add a selector for users to identify themselves. If they are not going to use same credentials, create a base view for common fields, then create separate signup views inheriting from that base view.
You need to extend User to add extra fields such as is_teacher (though I recommend you use CharField with choices so that you can add extra types of users in the future), there is a couple of ways of doing this explained elaborately in Django documentation, in your case setting up a custom user model via AbstractUser seems the best as I predict you will be extending that model further.
You can use UserPassesTestMixin or user_passes_test decorator to conditionally alter views for different types of users.

Non-db fields for Django model or admin

I have a model, which has some fields stored in db. On top of it, I need to implement non-db fields, which would be loaded and saved using a custom API.
Users should interact with the model using the admin interface, Grappelli is used to enhance the standard Django admin.
I am interested in one of the following:
Model virtual fields or properties, where I can override how to read and save custom fields. (Simple python properties won't work with Django admin)
Editable callables for admin (not sure if it is even possible)
Any other means to display and process custom fields in admin, except of creating custom forms and moving the logic into the forms.

I think you can use a none-model class, which wrapper the Model class and have some extra fields, where you can set/get or save to other place

Django form to create several objects with one-to-one relation

I have several models with one-to-one relation. For example
class Task(models.Model):
initial_comment = models.OneToOneField('Comment')
# A pack of other fields
class Comment(models.Model)
body = RichTextField()
# A pack of other fields
I want to create "create view" based on form, that gives user ability to create task and initial comment there.
I can't use CreateView because it is based on only one model
I can't use ModelForm because it is based on only one model
I can create several forms, but I can't join them into one formset (forms are different)
I feel "inlineformset_factory" (InlineFormSet) should be used here, but I am not sure it suits best. Is there any 3rd party Django app to do that?
Sure I can create form myself, but I do not want to copy/paste all fields, their types, localized labels, validations and so on. I just want to list their names (like fields attibute).
I can also have 2 forms and support them everywhere and track dependencies manually (save comments first), like in How can create a model form in django with a one-to-one relation with another model , but I hope there has to be better solution.
If you wonder why do I need one-to-one: Comments are used heavily in other places and have different relations with different models.

The inline_formset factory is correct. There are no standard generic views for this, but there is a third party package with generic views to do what you are wanting. Its in the standard Django way of doing things.
https://github.com/AndrewIngram/django-extra-views
You probably want to use the CreateWithInlinesView for that.

Well, I found solution.
CreateWithInlinesView works perfectly with OneToOneField (after all, 1-to-1 is just a foreign key with constraint), but my main model here is Comment, not Task. So I should set Comment as model field in this view and Task as inline. It looks silly. I will create custom form or review my model structure.

Should I use my own users table or use the admin generated one with django?

I created my own user table. I've been learning how to use the admin panel and I saw there's already a user table.
Should I use it or mine? (for example connection, member panel etc...)
If I should use it how to update it?
If I shouldn't what do I have to use it for?

Use the one django provides.
If you want extra fields on your user, create an extension to the user model.
It's really easy to do, you can just create your own model and make it inherit from the django.contrib.auth.User model, or you can also look here:
Extending the User model with custom fields in Django for more awesome answers of how people are doing this exact thing

Create new foreign key in form

I'm using django autocomplete_light and have two models connected via one-to-many relationship. Model A has a ForeignKey field TAG to model B. It all works, but I can only select the existing Tag, it is not possible to automatically add new Tag, even though it is possible to freely type in the box.
How can I "intercept" validation and create the suitable database entry for tag in time?

You could use an add another popup like in django admin.
Here's a live example using this code. The design is not very very good but it demonstrates the point.