Django Basics

https://developer.mozilla.org/en-US/docs/Learn/Server-side/Django/Introduction

What is django?

: Python web framework

• High-level Python web framework that enables rapid development of secure and maintainable websites

• Free & open source

web framework

• Aims to reduce difficulties encountered in web page development process

• A collection of classes and libraries that implement the standard structure of applications

Why do we have to learn django?

1. Portable

   • Python based which means it runs on many platforms

2. Complete

   • Django follows the "Batteries included" philosophy

     • Everything you need is part of the one "product"

     • Works seamlessly together

     • Follows consistent design principles

     • Has extensive and up-to-date documentation.

3. Versatile

   • Can be used to build almost any type of website

     • Can work with any client-side framework

     • Can deliver content in almost any format (including HTML, RSS feeds, JSON, XML, etc)

4. Secure

   • Provides a secure way to manage user accounts & passwords

     • By avoiding common mistakes like putting session information in cookies where it is vulnerable

       • Instead cookies just contain a key

       • And the actual data is stored in the db

     • By avoiding directly store passwords rather than password hash

5. Scalable

   • Uses a component-based "shared-nothing" architecture

     • each part of the architecture is independent of the others

     • can be replaced or changed if needed

   • Can scale for increase traffic by adding hardware at any level

     • caching servers

     • database servers

     • application servers

6. Maintainable

   • Follows DRY (Don't Repeat Yourself) principle

     • No unnecessary duplication

   • Promotes the grouping of related functionality into reusable

7. Many companies are utilizing it

   • Spotify

   • Instagram

   • Dropbox

   • Delivery Hero

   • etc.

Web protocol we know

• Request

• Response

How does django work?

• Django follows the MVC (Model View Controller) pattern.

  • MVC: One of the Software design patterns

    MVC Pattern	django
    Model	Model
    View	Template
    Controller	View

• MTV

  • M: Data management

  • T: Interface (screen)

  • V: Intermediate management (interaction)

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Run django on CS 50 IDE

CS 50 IDE

: CS50 IDE is a cloud-based Integrated Development Environment powered by AWS Cloud9 that features a cloud-based Ubuntu environment, a browser-based editor that supports syntax highlighting and word completion, a GUI-based GDB debugging, themes, customizable layouts, keyboard shortcuts, and many more features. Since it's cloud-based, you can continue working on your problem sets even if you use a different computer!

AWS Cloud 9

Cloud-based IDE (Integrated Development Environment)

• OS: Ubuntu 18.04.4 LTS

  • python 3.7.6

• Advantage of not affecting the local development environment

image-20200326100727731

Django installation

$ pip install django==2.1.15

• Download version 2.1.15

Django uninstall

$ pip uninstall django

Create project

$ django-admin startproject {project name}

Run server

• Edit line 28 of settings.py

ALLOWED_HOSTS = ['*']

• Always check the directory where the command is executed when running the server

$ cd djanggo_intro/
$ ls
$ python manage.py runserver 8080

• For the running server, click the URL in the right area

  

  image-20200326102907761
• To stop the server, use ctrl + c in terminal

Server running screen

image-20200326102049790

Create app

$ python manage.py startapp pages

Start Project

$ django-admin startproject first_django

• project is the atomic unit of Django!

Created project folder structure

image-20200326122807719

Create Pages

$ python manage.py startapp pages

Git

$ git init
$ ls -al
$ rm -rf .git

INSTALLED_APPS

: Registration

image-20200326131656480

• Added pages for registration

Start Server

$ python manage.py runserver 8080

image-20200326124046226

Check Port Number

$ echo $PORT
8080

• Can confirm connection to ports 80 and 8080

Check IP

$ echo $IP
127.0.0.1

Django has DEBUG=True as default

urls.py

Gatekeeper

from django.contrib import admin
from django.urls import path

urlpatterns = [
    path('request URL/', handling view(controller) function)
    path('admin/', admin.site.urls),
]

• path('request URL/', handling view(controller) function)

  • Django's characteristic is that URLs end with /!

pages/views.py

from django.shortcuts import render

# Create your views here.

def hello():
    return render(request,'HTML file name')

• Every time hello() is called, the object that called the function enters as the first argument

  • When defining a function in view, always define the first argument as request!

def lotto(request):
    import random
    pick = random.sample(range(1,46),6)
    context = {'pick':pick}
    return render(request, 'lotto.html', context)

• First argument - request

• Second argument - file name

• Third argument - context

  • Context must always be a dictionary!

Create pages/templates folder

• The name must be templates

Kill running python files

$ killall python
$ killall python3

Wrap-up

App Creation

• Django consists of one project with multiple apps

  • ex) Creating a community

    • App related to members - accounts

    • App related to posts - posts

$ python manage.py startapp {app name}

• After creating an app, must register it in INSTALLED_APPS in settings.py

  INSTALLED_APPS = [
      ...
      'pages',
  ]

Basic Flow

1. URL Configuration

• urls.py

  # django_intro/urls.py
  from pages import views
  
  urlpatterns = [
      path('lotto/', views.lotto),
  ]

  • URLs in path are always closed with /

2. View Configuration

• views.py

  # pages/views.py
  
  import random
  def lotto(request):
      pick = random.sample(range(1,46),6)
      context = {
          'pick': pick
      }
      return render(request, 'lotto.html', context)

• When defining functions, always write the first argument as request

  • Why? Because internally when processing requests, it needs to send an object containing request information when calling functions

• Return through render function

  • First argument: request

  • Second argument: template file (html)

  • Third argument

    • dictionary type

    • Pass values to be used in template

3. Create templates file

• The html file to return is always created inside the templates folder