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Django overview
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The following picture describes the mechanism of Django :

.. image:: django_steps.png


..  _django_overview:

Overview of Django configuration
======================================================

On the Django installation the following directories are created :


.. code-block:: bash

    myprojectdir
    ├── manage.py       #django utility to manage Django apps
    ├── myprojectenv    #python virtual environment used for Django framework and associated modules
    ├── myproject       #Django installation level directory containing common ressources for all projects 
    ├── static          #Django installation level directory containing static *.css, *.js, *.png, ... files for all projects


The ``myproject`` directory created automatically at install time contains the following :

.. code-block:: bash

    myprojectdir
    ├── manage.py       
    ├── myprojectenv    
    ├── myproject              #parent Django project containing common ressources for all projects 
        ├── __init__.py        #special Python file that indicates that the parent directory should be treated as a Python package
        ├── __pycache__        #created on first Python code execution and used in subsequent executions so that the program starts faster
        ├── asgi.py            #asychronous processing equivalent to WSGI used to manage the server side invoking a callable object
        ├── settings.py        #contains all the configuration of the Django installation
        ├── urls.py            #contains all mappings between URLs, that the Django installation serves, and Python views. All URLs of all Django apps need to be declared here
        ├── wsgi.py            #Web Server Gateway Interface to process non static requests such as Python code that need to be executed on server side 


When a new Django app is launched using the ``manage.py`` command, the ``django_app`` directory is created automatically at the same level as the directory ``myproject`` and will have the following hierarhy :

.. code-block:: bash

    myprojectdir
    ├── manage.py       
    ├── myprojectenv    
    ├── myproject 
    ├── static
    ├── django_app            #directory for each individual Django app 
        ├── __init__.py       #special Python file to indicate the directory should be treated as Python package
        ├── __pycache__       #python cache
        ├── admin.py          #django app admin utility used to customize and configure the Django admin interface for managing models in Django project 
        ├── apps.py           #used to configure the application and define application-specific settings and metadata
        ├── migrations        #when changes are done in the database, Django can automatically generate migration files that represent those changes
        ├── models.py         #central component of each Django app, where data models for the application are defined
        ├── templates         #used to store HTML template files that define the structure and layout of the user interface for the web application
        ├── tests.py          #used to write unit tests for the Django application
        ├── urls.py           #used to define URL patterns for the web application
        ├── views.py          #used to define the view functions or classes that handle HTTP requests and generate HTTP responses for the web application



..  _activate_virtual_env:

Activate virtual env
======================================================
To use Django command line, activate the virtual environement

.. code-block:: bash

    usr1@server:~/myprojectdir$ source myprojectenv/bin/activate

The prompt is changed as follows 

.. code-block:: bash

    (myprojectenv) usr1@server:~/myprojectdir$

..  _create_new_django_app:

Create new Django app
======================================================


We can now execute Django instructions. To create a new Django app, use the ``manage.py`` command.

.. code-block:: bash

    (myprojectenv) usr1@server:~/myprojectdir$ python3 manage.py startapp demo1

This results in the creation of a directory named ``demo1`` with the following hierarchy.

.. code-block:: bash

    myprojectdir
    ├── manage.py       
    ├── myprojectenv    
    ├── myproject 
    ├── static
    ├── demo1                 #directory for each individual Django app 
        ├── __init__.py       #special Python file to indicate the directory should be treated as Python package
        ├── __pycache__       #python cache
        ├── admin.py          #django app admin utility used to customize and configure the Django admin interface for managing models in Django project 
        ├── apps.py           #used to configure the application and define application-specific settings and metadata
        ├── migrations        #when changes are done in the database, Django can automatically generate migration files that represent those changes
        ├── models.py         #central component of each Django app, where data models for the application are defined
        ├── templates         #used to store HTML template files that define the structure and layout of the user interface for the web application
        ├── tests.py          #used to write unit tests for the Django application
        ├── urls.py           #used to define URL patterns for the web application
        ├── views.py          #used to define the view functions or classes that handle HTTP requests and generate HTTP responses for the web application