#Django

##What is Django?

Django is a free and open source web application framework, written in Python. It's a web framework - a set of components that helps you to develop websites faster and easier.

====================================================================

##Installation (OS X)

Python is native in your machine, but you will need to check which version are you actually using. For this tutorial you will need a from version 3.4 onward.

To check your version:

python3 --version

The reason why you will need from version 3.4 on, is because you will be using the pip command (the python version of npm).

If you want to download the latest version, visit the official Python website

##Virtual Environment & Django installation

A Virtual Environment is a tool to keep the dependencies required by different projects in separate places, by creating virtual Python environments for them (check your folder structure after typing the following command). It's possible to skip this step, but it's highly recommended not to - starting with the best possible setup will save you a lot of trouble in the future!(TRUE, TRUE, TRUE, TRUE!!)

Move into your project directory and run this command:

python3 -m venv myvenv

where myenv is a customizable parameter that refers to the name of your virtual env. (HINT: keep it short because you will be referencing it a lot.)

Then, to activate your virtualenv, just type:

source myvenv/bin/activate

As a result, you will see your prompt looking something like:

(myvenv) ~/djangogirls$

If you want to commit those stages to GitHub, remember to disactivate your virtualenv by typing:

deactivate

Now, your are finally ready to install Django. Just type (in your virtualenv):

pip install django==1.7.1

====================================================

##Starting the actual project

In your virtualenv, type:

django-admin startproject mysite .

This command will create a huge file structure and a mysite folder with the following structure:

mysite/
├── __init__.py
├── settings.py
├── urls.py
└── wsgi.py

manage.py is a script that helps with management of the site. With it we will be able to start a web server on our computer without installing anything else, amongst other things.

settings.py contains the config of the website.

====================================

##Creating an app

From the location in which your manage.py seats, type:

python manage.py startapp blog

This command will create a blog app folder with this structure:

└── blog
    ├── migrations
    |       __init__.py
    ├── __init__.py
    ├── admin.py
    ├── models.py
    ├── tests.py
    └── views.py

Now, we need to tell Django that we want to use our blog app. In mysite/settings.py under INSTALLED_APPS add 'blog':

INSTALLED_APPS = (
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'blog',
)

==========================================================

###Creating a BlogPostModel

Open blog/models.py and type:

from django.db import models
from django.utils import timezone

class Post(models.Model):
    author = models.ForeignKey('auth.User')
    title = models.CharField(max_length=200)
    text = models.TextField()
    created_date = models.DateTimeField(
            default=timezone.now)
    published_date = models.DateTimeField(
            blank=True, null=True)

    def publish(self):
        self.published_date = timezone.now()
        self.save()

    def __str__(self):
        return self.title

This will allow us to create new Posts. Now we need to tell Django about those changes and that we want to use them for our db. Just type:

python manage.py makemigrations blog

This will create some migrations files (as in Rails with the schema) that now we need to apply to the db:

python manage.py migrate blog

=================================================

##Django Shell and QuerySet

To access the Django Shell, just type:

python manage.py shell

Now you can use all the properties of QuerySet. A QuerySet is, in essence, a list of objects of a given Model and it allows you to read the data from database, filter it and order it.

You first need to import Post and User. For the first, type:

from blog.models import Post

while for the second one, insert:

from django.contrib.auth.models import User

Now, if you type Post.objects.all() or User.objects.all() you will see: [] because they both exist but they are empty. So, let's populate them. First, we will create a new User by typing:

User.objects.create(username='giorgia')

then, we can create an instance of user:

me = User.objects.get(username='giorgia')

Now, is time to create our first Post:

Post.objects.create(author = me, title = 'Sample title', text = 'Test')

and now, if you type Post.objects.all(), you will see your first Post: [<Post: Sample title>]

===================================================