Introduction to Django Programming: Understanding Python's Web Framework

With the popularity of the Internet, more and more people are beginning to transition to Web development. The Python language has gradually become one of the mainstream languages ​​​​in the field of web development because of its characteristics such as easy to learn, strong readability, and support for multiple programming paradigms. As a web framework for the Python language, Django provides powerful support for web development in the Python language and has become the first choice of many developers. This article will introduce the relevant knowledge of Django starting from the basic concepts to help beginners quickly understand the introduction to Django programming.

1. The origin and overview of Django

Django is an open source web framework created by Adrian Holovaty and Simon Willison in 2003 during the process of producing news websites for newspapers. The main feature of Django is to follow the MVC pattern to improve the maintainability and scalability of web applications. It is a highly modular framework that includes functions such as ORM, template engine, form processing, etc.

The latest version of Django is 3.2.6, which provides many new features and improvements. For example, asynchronous views and ASGI are supported, foreign key fields use the UUID type by default, JSONField and ArrayField types are added, and request headers can be obtained through the headers attribute of the HttpRequest object, etc. In general, Django provides developers with rich functions and convenient development methods, making web application development more efficient and faster.

2. Basic concepts of Django

1. Routing (URLconf): Django’s URLconf is a URL configuration file that maps the URL requested by the browser to the corresponding view function. By default, the URLconf is located in the project's urls.py file.
2. Views: Views are where business logic is implemented in Django applications. They handle user requests and return responses. The view can be a function view or a class view. Generally, we will use the class view.
3. Templates: Templates are files required to render the data returned by the view into an HTML page. Django provides a built-in template engine that supports template inheritance, template tags, filters and other functions.
4. ORM (Object Relation Mapping): ORM is a technology that maps objects to database tables. It allows developers to operate the database in an object-oriented manner. Django's ORM is called Models. Models use classes to define database tables, and operations such as adding, deleting, modifying, and querying data can be performed through model classes.
5. Form processing (Forms): Django's form processing is a fast and safe way to process user input form data. The form class is associated with the view function so that data is written to the database after the form is validated.

3. Django installation and project creation

1. Install Django: Django can be installed through pip. You can use the command pip install django to install the latest version of Django.
2. Create project: Django projects can be created using the django-admin startproject command, for example:

django-admin startproject mysite

This command will create a project directory and file named mysite, which contains a A management script called manage.py and a Django package called mysite.

3. Run the server: Execute the following command to run the server:

python manage.py runserver

4. Django routing and views

1. Routing: In Django , routes are defined using URLconf. Map URL patterns to view functions using a regular expression and the view function name as arguments. For example, here is a URL pattern that contains a view function:

from django.urls import path
from . import views

urlpatterns = [
    path('hello/', views.say_hello),
]

2. View: In Django, a view is usually a function or class that receives an HTTP request and returns an HTTP response. Here is a simple view function:

from django.http import HttpResponse

def say_hello(request):
    return HttpResponse('Hello Django!')

The above code will return an HTTP response containing the "Hello Django!" message.

5. Django’s template and form processing

1. Template: Django provides a built-in template engine, which can use familiar HTML syntax to write templates. Templates can use features such as variables, tags, and filters in the Django Template Language (DTL). Here is a simple template example:

<!DOCTYPE html>
<html>
<head>
    <title>{{ title }}</title>
</head>
<body>
    <h1 id="title">{{ title }}</h1>
    <p>{{ content }}</p>
</body>
</html>

2. Form processing: Django's form processing is a fast and safe way to process user input form data. The following is an example of a form class:

from django import forms

class ContactForm(forms.Form):
    name = forms.CharField(label='Your name', max_length=100)
    email = forms.EmailField(label='Email address')
    message = forms.CharField(widget=forms.Textarea)

The above code will create a ContactForm class for collecting contact form information submitted by users.

6. Summary

As a powerful Web framework, Django provides strong support for Web development in Python language. With its high scalability, high modularity, ORM and other characteristics, it has become one of the preferred frameworks for developers to develop medium and large-scale web applications. This article briefly introduces Django's overview, basic concepts, installation and creation, routing and views, templates and form processing, etc., for beginners to learn and refer to.

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