Master Django Basics: From Project Setup to Models and Forms

1. Introduction

Django is an open‑source web application framework written in Python that follows the MVC (model‑view‑controller) design pattern and powers many successful websites and apps.

2. Key Features

Powerful ORM: define database tables with Python classes and perform queries with a high‑level API, while still allowing raw SQL.

Built‑in admin interface: generate a full‑featured administration site with just a few lines of code.

Elegant URL routing: map URLs to view functions using regular expressions.

Extensible template system: separate HTML presentation from Python logic.

Cache integration: work with memcached or other back‑ends for faster response times.

Internationalization: full support for multiple languages and translations.

3. Project Layout

urls.py

: URL entry point that links patterns to view functions or class‑based views. views.py: Handles requests, renders templates, and returns responses. models.py: Defines data models and interacts with the database. forms.py: Defines form fields, validation, and rendering (optional). templates/ folder: Stores HTML templates used by views. admin.py: Registers models for the automatic admin site. settings.py: Configuration file (DEBUG flag, static files, etc.).

4. Basic Commands

Start a new project: django-admin startproject project-name Create a new app: python manage.py startapp app-name (or django-admin startapp app-name)

Run the development server: python manage.py runserver 0.0.0.0:8000 (accessible from other machines) or python manage.py runserver (local only).

5. Views and URLs

Example view returning a simple string:

from django.http import HttpResponse

def helloWorld(request):
    return HttpResponse("Hello world! ")

Corresponding URL pattern:

from django.conf.urls import url
from . import view

urlpatterns = [
    url(r'^$', view.helloWorld),
]

After adding a path segment:

urlpatterns = [
    url(r'^helloWorld$', view.helloWorld),
]

Access the view at http://127.0.0.1:8000/helloWorld.

6. Templates

Place helloWorld.html in the app’s templates folder:

<h1>{{ helloWorld }}</h1>

Tell Django where to look for templates by adding the directory to TEMPLATES['DIRS'] in settings.py:

TEMPLATES = [{
    ...
    'DIRS': [BASE_DIR + "/templates",],
    ...
}]

Render the template from a view:

from django.shortcuts import render

def hello(request):
    context = {'helloWorld': 'Hello World!'}
    return render(request, 'helloWorld.html', context)

Template tags such as {% if %}, {% for %}, {% include %}, and filters like {{ name|lower }} are supported.

7. Models and Database

Example model using MySQL:

from django.db import models

class Test(models.Model):
    name = models.CharField(max_length=20)

Database configuration in settings.py:

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.mysql',
        'NAME': 'test',
        'USER': 'test',
        'PASSWORD': 'test123',
        'HOST': 'localhost',
        'PORT': '3306',
    }
}

Typical migration commands:

python manage.py makemigrations TestModel
python manage.py migrate TestModel

Basic CRUD operations demonstrated with HttpResponse views that create, read, update, and delete Test objects.

8. Forms (GET and POST)

GET form example:

from django.http import HttpResponse
from django.shortcuts import render_to_response

def search_form(request):
    return render_to_response('search_form.html')

def search(request):
    request.encoding = 'utf-8'
    if 'q' in request.GET:
        message = '搜索的内容为: ' + request.GET['q']
    else:
        message = '提交了空表单'
    return HttpResponse(message)

Corresponding search_form.html contains a simple <form> with a text input named q.

POST form example (requires CSRF token):

from django.shortcuts import render

def search_post(request):
    ctx = {}
    if request.POST:
        ctx['rlt'] = request.POST['q']
    return render(request, 'post.html', ctx)

URL patterns are extended to include the new view:

urlpatterns = [
    url(r'^search-form$', search.search_form),
    url(r'^search$', search.search),
    url(r'^search-post$', search2.search_post),
]