Django

Django is a high-level Python web framework that encourages rapid development and clean, pragmatic design. Built by experienced developers, it takes care of much of the hassle of web development, so you can focus on writing your app without needing to reinvent the wheel. It’s free and open source

Models:

A model is the single, definitive source of information about your data. It contains the essential fields and behaviors of the data you’re storing. Generally, each model maps to a single database table.

• Each model is a Python class that subclasses django.db.models.Model.

• Each attribute of the model represents a database field.

• With all of this, Django gives you an automatically-generated database-access API

EX:

from django.db import models

class Person(models.Model):
    first_name = models.CharField(max_length=30)
    last_name = models.CharField(max_length=30)

Once you have defined your models, you need to tell Django you’re going to use those models. Do this by editing your settings file and changing the INSTALLED_APPS setting to add the name of the module that contains your models.py.

For example, if the models for your application live in the module myapp.models (the package structure that is created for an application by the manage.py startapp script)

Fields

The most important part of a model – and the only required part of a model – is the list of database fields it defines. Fields are specified by class attributes. Be careful not to choose field names that conflict with the models API like clean, save, or delete.

from django.db import models

class Musician(models.Model):
    first_name = models.CharField(max_length=50)
    last_name = models.CharField(max_length=50)
    instrument = models.CharField(max_length=100)

class Album(models.Model):
    artist = models.ForeignKey(Musician, on_delete=models.CASCADE)
    name = models.CharField(max_length=100)
    release_date = models.DateField()
    num_stars = models.IntegerField()

Field types

Each field in your model should be an instance of the appropriate Field class. Django uses the field class types to determine a few things

• The column type, which tells the database what kind of data to store .

• The default HTML widget to use when rendering a form field

• The minimal validation requirements, used in Django’s admin and in automatically-generated forms.

The Django admin site

One of the most powerful parts of Django is the automatic admin interface. It reads metadata from your models to provide a quick, model-centric interface where trusted users can manage content on your site. The admin’s recommended use is limited to an organization’s internal management tool. It’s not intended for building your entire front end around.

ModelAdmin objects

The ModelAdmin class is the representation of a model in the admin interface. Usually, these are stored in a file named admin.py in your application. Let’s take a look at an example of the ModelAdmin:

from django.contrib import admin
from myapp.models import Author

class AuthorAdmin(admin.ModelAdmin):
    pass
admin.site.register(Author, AuthorAdmin)

ModelAdmin.fieldsets

Set fieldsets to control the layout of admin “add” and “change” pages.

fieldsets is a list of two-tuples, in which each two-tuple represents a fieldset on the admin form page. (A fieldset is a “section” of the form.)

The two-tuples are in the format (name, field_options), where name is a string representing the title of the fieldset and field_options is a dictionary of information about the fieldset, including a list of fields to be displayed in it.

from django.contrib import admin

class FlatPageAdmin(admin.ModelAdmin):
    fieldsets = (
        (None, {
            'fields': ('url', 'title', 'content', 'sites')
        }),
        ('Advanced options', {
            'classes': ('collapse',),
            'fields': ('registration_required', 'template_name'),
        }),
    )