URL name

1. DB

DB initialization

1. Delete db.sqlite3

2. Delete migration files

Check migration files

python manage.py showmigrations

Create migrations again

python manage.py makemigrations

Output corresponding SQL statement

$ python manage.py sqlmigrate articles 0001
       [app_label] [migration_name]
BEGIN;
--
-- Create model Article
--
CREATE TABLE "articles_article" ("id" integer NOT NULL PRIMARY KEY AUTOINCREMENT, "title" varchar(140) NOT NULL, "content" text NOT NULL, "created_at" datetime NOT NULL, "updated_at" datetime NOT NULL);
COMMIT;

Run migrate

$ python manage.py migrate
  [app_label] [migration_name]

create()

For creation, you can also do it as follows!

Article.objects.create(title='title', content='content')

article = Article(title='title', content='content')
article.save()

IntegrityError

: This exception is raised when the relational integrity of the data is affected.

2. GET & POST method

• GET

  • Retrieve data

  • Display of specific resources

  • <a> tag, <form> tag and requests sent from browser address bar, etc.

  • Data is transmitted using URL (querystring)

    • Has size limitations & security issues

• POST

  • Post data

  • Submit to specific resources (server state change)

  • Usually sent to server through HTML Form, creating server changes

  • Data is transmitted in the body of HTTP request message

HTTP (Hyper Text Transfer Protocol)

• Protocol that allows resources to be fetched

• Foundation of all exchanges on the web

Request

HTTP Request

• URL (Uniform Resource Locators)

  • Address of unique resource defined on the web

• protocol :// domain: port/ path/?parameters#anchor

Response

HTTP Response

views.py modification

def create(request):
    article = Article()
    article.title= request.POST.get('title')
    article.content = request.POST.get('content')
    article.save()
    return redirect(f'/articles/{article.pk}/')

Adding CSRF token

<form action="/articles/create/" method="POST">
    {% csrf_token %}
</form>

You can see that csrf token is added as a hidden value

CSRF Token

Send simple request with Curl

curl -X GET http://chloecodes1.pythonanywhere.com/community/

Using Telnet

Installation

sudo apt-get install telnetd

Send request

telnet google.com 80

3. Specifying app_name

urls.py

from django.urls import path
from . import views

app_name = 'articles'

urlpatterns = [
    # /articles/
    path('', views.index, name='index'),
    path('new/', views.new, name='new'),
    path('create/',views.create, name='create'),
    path('<int:pk>/',views.detail, name='detail'),
    path('delete/<int:pk>/',views.delete, name='delete'),
    path('edit/<int:pk>/', views.edit, name='edit'),
    path('update/<int:pk>/', views.update, name='update'),
]

views.py

from django.shortcuts import render, redirect, get_object_or_404
from .models import Article

# Create your views here.

def index(request):
    articles = Article.objects.all()
    context = {
        'articles': articles
    }

    return render(request, 'articles/index.html', context)

def new(request):
    return render(request, 'articles/new.html')

def create(request):
    article = Article()
    article.title= request.POST.get('title')
    article.content = request.POST.get('content')
    article.save()

    # return redirect(f'/articles/{article.pk}/')
    return redirect('articles:detail', article.pk)


def detail(request, pk):
    article = Article.objects.get(id=pk)
    context = {
        'article':article
    }
    return render(request,'articles/detail.html', context)


def delete (request, pk):
    article = Article.objects.get(id=pk)
    article.delete()

    # return redirect(f'/articles/')
    return redirect('articles:index')


def edit(request, pk):
    article = get_object_or_404(Article, id = pk)
    context = {
        'article': article
    }

    return render(request, 'articles/edit.html', context)

def update (request,pk):
    article = Article.objects.get(id=pk)
    article.title = request.POST.get('title')
    article.content = request.POST.get('content')
    article.save()

    return redirect(f'/articles/{article.pk}/')

In html

<a class="navbar-brand" href="{% url 'articles:index' %}"> ... </a>

<a href="{% url 'articles:delete' article.pk %}"> ... </a>

<form class="form-inline" action="{% url 'articles:search' %}" method="POST"> ... </form>

4. get_object_or_404

article = Article.objects.get(id=pk)

• get() raises error if value doesn't exist

  • Method that returns only one

• So what we use is

  from django.shortcuts import render, redirect, get_object_or_404
   ...
  article = get_object_or_404(Article, id=pk)

5. Static files

settings.py

# Attached in front of serving URL
STATIC_URL = '/static/'

# Specify static folder not in app directory
STATICFILES_DIRS = [
    os.path.join(BASE_DIR, 'static')
]

+

Traceroute

TraceRoute - Linux / TRACERT - Windows

A command that tracks the path information to reach a specified host and the delay time at each path, simply think of it as a path tracking tool (uses ICMP!)

• A network command that tracks path information to reach a specified host and delay time at each path, useful for finding out where bottlenecks occur when a specific site is not accessible or has delays.

• By checking each path that gets connected, you can confirm which path (Routing) is used for connection, how much speed delay exists in which section, and where packets stopped

• However, values may vary due to many influences such as time zone/internal traffic/server status, so repeated confirmation is necessary!

Install traceroute

sudo apt-get install traceroute

Use traceroute

$ traceroute www.google.com
traceroute to www.google.com (172.217.31.164), 30 hops max, 60 byte packets
 1  _gateway (172.30.1.254)  5.195 ms  5.127 ms  5.105 ms
 2  220.78.3.1 (220.78.3.1)  5.071 ms * *
 3  125.141.249.21 (125.141.249.21)  5.364 ms  5.308 ms  5.262 ms
 4  * * *
 5  * * *
 6  112.174.73.178 (112.174.73.178)  6.510 ms 112.174.47.162 (112.174.47.162)  5.301 ms 112.174.73.178 (112.174.73.178)  4.858 ms
 7  74.125.52.16 (74.125.52.16)  31.913 ms  31.801 ms  33.951 ms
 8  108.170.242.129 (108.170.242.129)  36.142 ms 108.170.242.97 (108.170.242.97)  34.386 ms  34.811 ms
 9  209.85.253.109 (209.85.253.109)  36.711 ms  36.555 ms  36.483 ms
10  nrt12s22-in-f4.1e100.net (172.217.31.164)  34.998 ms  33.267 ms  32.844 ms

MVC Pattern

• model driven design

• data modeling