Notes Re Django Documentation

Models

a model is like a column/row/table of an excel file, it contains essential fields and behaviours of the data stored
they all inherite django.db.models.Model class
after setting up the model classes, you can access the database through the API generated automatically by Django: see Making queries
Adding apps to settings INSTALLED_APPS: this is to tell Django that there’s new models you’d like to use and you’ve set them up, after that, you need to makemigrations and migrate for the models to take effect, meaning tables are created in the database for you to use later
Model fields: determine the column type, the default HTML widget to use to render a form field, validation; model field reference lists all the fields a model class can implement
Field common used options:
- null=True, database related, doesn’t have to exist at all
- blank=True(can be not filled), validation on forms won’t be required
- choices=((‘s’, ‘small’), (‘m’, ‘medium’), (‘l’,’large’)) a sequence of 2-tuples,
- default: a value or a callable object, everytime the new object is created, it will be called
- unique=True, this field must be unique throughout the table common model field option reference
Model Meta options
Model methods: define functions/methods on a model is adding custom “row-level” functionality to the object.
Model inheritance:

filters: Retrieving specific objects with filters
Entry.objects.all()[:5] - first 5 entry objects (LIMIT 5)
Entry.objects.all()[5:10] - (OFFSET 5 LIMIT 5)
Entry.objects.all()[:10:2] - return a list of every second object of the first 10
chaning filters: The result of refining a QuerySet is itself a QuerySet, so it’s possible to chain refinements together. For example:
```
>>> Entry.objects.filter(
...     headline__startswith='What'
... ).exclude(
...     pub_date__gte=datetime.date.today()
... ).filter(
...     pub_date__gte=datetime.date(2005, 1, 30)
... )
```
This takes the initial QuerySet of all entries in the database, adds a filter, then an exclusion, then another filter. The final result is a QuerySet containing all entries with a headline that starts with “What”, that were published between January 30, 2005, and the current day.

\<slug:slug\> at the end of url dispatcher: matches any slug string consiting of ASCII letters or numbers, plus the hyphen and underscore characters.
from django.urls import re_path for regex: re_path(r'^articles/(?P<year>[0-9]{4})/$', views.year_archive),)
you can pass extra options to view function: here

To be read