Starting a Django project

Install Django

conda install django
python -m django --version

Create a project
```
mkdir project_folder
cd project_folder
django-admin startproject travelclean_gui
```
Create a secret file:
You need to redo this step when cloning the repository.

This creates a skeleton folder structure.
- The main settings are stored in a folder called "travelclean_gui".
  - settings.py
  - urls.py
  - asgi.py
  - wsgi.py
- manage.py does most command line management
Start the development server
```
python3 manage.py runserver
```
This is always useful during development
Create a new app
```
python manage.py startapp cars
```
This creates a folder named "cars". The folder contains
- models.py:
  - Models map tables in the database to Python classes
- views.py:
  - Urls are mapped to views
  - Views return html, which is sent to the client
- urls.py
  - mapping of urls to views (can be done in travelclean_gui/urls.py)
- admin.py
  - for managing the admin interface
- tests.py
  - test for the models, views, forms
- apps.py
- migrations
  - managed by Django
Add the new app to "travelclean_gui/settings.py":
```
INSTALLED_APPS = [
    'polls.apps.PollsConfig',
    ...
    'cars',
]
```
Add a superuser
```
python manage.py createsuperuser
```
The superuser has access to the admin pages. Check out http://0.0.0.0:8000/admin.

Add a model (data in the database)

cars/models.py

from django.db import models

class Camera(models.Model):
    # Columns in the database table are members in the class
    description = models.CharField(max_length=200)
    ip = models.GenericIPAddressField(max_length=50)

You need to update the database to reflect the new model:

python manage.py makemigrations
python manage.py migrate

This will add the table into the database. It does not contain any data, since we didn't create a camera yet.

The easiest way to change the data is to add the model to admin:

cars/admin.py

from django.contrib import admin

from .models import Camera

admin.site.register(Camera)

Add a URL and view

travelclean_gui/urls.py:

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

urlpatterns = [
    path('', include('cars.urls')),
    path('admin/', admin.site.urls),
]

cars/urls.py:


from django.urls import path

from . import views

urlpatterns = [
    path('', views.index, name='index'),
]

cars/views.py

from django.http import HttpResponse

def index(request):
    return HttpResponse("Hello!")

This view just returns text, but it's general python code, so it could be anything more complicated.
Django has a powerful templating system, that makes this a lot easier.

Add a view to interact with the model

cars/urls.py

from django.urls import path

from . import views

urlpatterns = [
    path('', views.index, name='index'),
    path('cameralist', views.CameraListView.as_view(), name='camera_list'),
    path('camera/<pk>', views.CameraDetailView.as_view(), name='camera'),
]

cars/views.py

from django.shortcuts import render
from django.http import HttpResponse
from django.views import generic

from .models import Camera


# Create your views here.

def index(request):
    return HttpResponse("Hello!")

class CameraListView(generic.ListView):
    model = Camera
    template_name = 'camera_list.html'
    
class CameraDetailView(generic.DetailView):
    model = Camera

cars/templates/cars/camera_list.html

<html>  
<body>

    {% block content %}
    <h1>Camera List</h1>
       {% if camera_list %}
       <ul>
           {% for camera in camera_list %}
           <li>
              {{ camera.id }}: {{camera.description}}
           </li>
           {% endfor %}
      </ul>
      {% else %}
      <p>No cameras found</p>
      {% endif %}
   {% endblock %}
</body>
</html>

cars/templates/cars/camera_detail.html

<html>
<body>

    {% block content %}
    <h1>Camera</h1>

    {{ camera.id }}: {{camera.description}} : {{camera.ip}}

    {% endblock %}
</body>
</html>

There are a number of these generic views, see https://docs.djangoproject.com/en/3.2/topics/class-based-views/generic-display/

Add a form for changing the data
- In fact a view can change the data on post, but forms allow you to submit more structured data

Starting a Django project

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Collaborative exercises

Introduction to Julia

Introduction to Julia

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