tutorials

Creating a project

$ django-admin startproject mysite

Let’s look at what startproject created:

mysite/
    manage.py
    mysite/
        __init__.py
        settings.py
        urls.py
        wsgi.py

These files are:

The outer mysite/ root directory is just a container for your project. Its name doesn’t matter to Django; you can rename it to anything you like.

manage.py: A command-line utility that lets you interact with this Django project in various ways. 

The inner mysite/ directory is the actual Python package for your project. Its name is the Python package name you’ll need to use to import anything inside it (e.g. mysite.urls).

mysite/__init__.py: An empty file that tells Python that this directory should be considered a Python package. 

mysite/settings.py: Settings/configuration for this Django project. 

mysite/urls.py: The URL declarations for this Django project; a “table of contents” of your Django-powered site. 

mysite/wsgi.py: An entry-point for WSGI-compatible web servers to serve your project. 


The development server

Let’s verify your Django project works. Change into the outer mysite directory, if you haven’t already, and run the following commands:

$ python manage.py runserver

Now that the server’s running, visit http://127.0.0.1:8000/ with your Web browser. You’ll see a “Welcome to Django” page, in pleasant, light-blue pastel. It worked!


Changing the port

By default, the runserver command starts the development server on the internal IP at port 8000.

If you want to change the server’s port, pass it as a command-line argument. For instance, this command starts the server on port 8080:

$ python manage.py runserver 8080

If you want to change the server’s IP, pass it along with the port. For example, to listen on all available public IPs (which is useful if you are running Vagrant or want to show off your work on other computers on the network), use:

$ python manage.py runserver 0:8000
0 is a shortcut for 0.0.0.0


Automatic reloading of runserver

The development server automatically reloads Python code for each request as needed. You don’t need to restart the server for code changes to take effect. However, some actions like adding files don’t trigger a restart, so you’ll have to restart the server in these cases.


Projects vs. apps

What’s the difference between a project and an app? An app is a Web application that does something – e.g., a Weblog system, a database of public records or a simple poll app. A project is a collection of configuration and apps for a particular website. A project can contain multiple apps. An app can be in multiple projects.


Creating the Polls app

$ python manage.py startapp polls


polls/
    __init__.py
    admin.py
    apps.py
    migrations/
        __init__.py
    models.py
    tests.py
    views.py





The url() function is passed four arguments, two required: regex and view, and two optional: kwargs, and name. At this point, it’s worth reviewing what these arguments are for.


create the tables in the database before we can use them. To do that, run the following command:

$ python manage.py migrate


$ python manage.py makemigrations polls

By running makemigrations, you’re telling Django that you’ve made some changes to your models (in this case, you’ve made new ones) and that you’d like the changes to be stored as a migration.
Migrations are how Django stores changes to your models (and thus your database schema) - they’re just files on disk. 


The sqlmigrate command takes migration names and returns their SQL:

$ python manage.py sqlmigrate polls 0001

The sqlmigrate command doesn’t actually run the migration on your database - it just prints it to the screen so that you can see what SQL Django thinks is required. It’s useful for checking what Django is going to do or if you have database administrators who require SQL scripts for changes.


Table names are automatically generated by combining the name of the app (polls) and the lowercase name of the model – question and choice. (You can override this behavior.)

Primary keys (IDs) are added automatically. (You can override this, too.)

By convention, Django appends "_id" to the foreign key field name. (Yes, you can override this, as well.)

The foreign key relationship is made explicit by a FOREIGN KEY constraint


 $ python manage.py check

 this checks for any problems in your project without making migrations or touching the database.



The migrate command takes all the migrations that haven’t been applied (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.


remember the three-step guide to making model changes:

Change your models (in models.py).
Run python manage.py makemigrations to create migrations for those changes
Run python manage.py migrate to apply those changes to the database.

Creating an admin user¶

First we’ll need to create a user who can login to the admin site. Run the following command:

$ python manage.py createsuperuser
, http://127.0.0.1:8000/admin/. 


A view is a “type” of Web page in your Django application that generally serves a specific function and has a specific template.

In Django, web pages and other content are delivered by views. Each view is represented by a simple Python function (or method, in the case of class-based views). Django will choose a view by examining the URL that’s requested (to be precise, the part of the URL after the domain name).