# Django

Django request response lifecycle

# Features?

build a website with database attached to it

high level web framework with batteries included started in 2003
instagram, pinterest, dropbox
creating Django Data Models and then rendering them into Views. Full MVC pattern compliant
Free admin UI out of the box
single request/response model like PHP at a time, single threaded
Security against SQL injection, cross-site scripting, cross-site request forgery and clickjacking.
WSGI successor (PEP 333 & PEP 3333) => ASGI Asynchronous Server Gateway Interface
- Django Channels, Queue implementation
- CGI, run C code from HTTP requests
- before request/response now we are talking about connection and events
Can create and mount multiple apps under various urls paths, use include()

# startup commands
python -m venv venv && source ./venv/bin/activate
pip install django && django-admin startproject dj2021 && cd dj2021
# create local sqlite DB, run it anytime after to make new, change django models
python manage.py migrate
python manage.py runserver

django migrations

You have 18 unapplied migration(s). Your project may not work properly until you apply the migrations for app(s): admin, auth, contenttypes, sessions. Run 'python manage.py migrate' to apply them.

Migrations are Django’s way of propagating changes you make to your models (adding a field, deleting a model, etc.) into your database schema.

start development serverpython manage.py migrate && python manage.py runserver

Django tracks which ones are applied using a special table in your database called django_migrations) and runs them against your database - essentially, synchronizing the changes you made to your models with the schema in the database.

# New App

Django apps are more like components

python manage.py startapp <app_name>
python manage.py createsuperuser

Let django know about your new app model, wire up new app into django

# How to write views?

How to add App namespace?
Pass Template Context Variables to views
view templates can inherit other templates
Template Tags block and extends, if, for loop, filters stacking is possible
Cross reference and linking?
Namespace your local app URLs
class based views
How to Paginate data from models to views? from django.core.paginator import paginator
- page number from query string paginator.page(request.GET.get('page', 1))

# How to add new models?

changing Models

Anytime you change models, dont forget to run makemigrations and migrate

Add values to database directly from shell

python manage.py makemigrations polls
python manage.py migrate
python manage.py shell
python manage.py sqlmigrate polls 0001

Register your app models to admin admin.site.register(Question)
How to raise 404 ? when model doesnt exist? get_object_or_404

what is refential CASCADE in django models?: When the referenced object is deleted, also delete the objects that have references to it (when you remove a blog post for instance, you might want to delete comments as well). SQL equivalent: CASCADE.

Pull data from Models in Template Context?
QuerySet object.all()

# Deal with Forms? Capturing data

from django import forms

diff b/w ModelForms and Form? Validations provide by django
action and method, create your own google search form
Add security while using POST {% csrf_token %}
- user can clear up required from HTML form at client side and try to submit
- my_form.is_valid, my_form.clean_data
Initial data on form, default data

# How is it different?

Ruby of rails

twitter, shopify 14 years ago

# Django | node.js | ruby on rails

# production web-server | database

# postgresSQL vs mySQL

# How to work with django?

Write django queries
[ ] Create new App
[ ] Add apps to your django project
[ ] Create new models
[ ] Run migrations
[ ] Add model to admin
[ ] Create new views and send Template Context Variables to them
[ ] Forms and add Security

# Django Projects

https://github.com/techwithtim/Music-Controller-Web-App-Tutorial

# Quesstions

Django backend and react frontend
Backend for Mobile endpoints
hosting?

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