In-depth understanding of Python's Django framework

This article mainly introduces the Python code to implement the Django framework. The editor thinks it is quite good. Now I will share it with you and give it a reference. Let’s follow the editor and take a look.

1. URLconf

When the user accesses the URL through the browser to request the website, he finds the corresponding function through the URL for execution, and Django The url configuration in is configured in settings.py in the folder with the same name as the project

1, configuration

(1), test1/settings.py configuration file

settings.py has specified the url configuration through ROOT_URLCONF by default, pointing to the urls.py file under test1:

## (2), test1/ The configuration items in urls.py are as follows:

Note:

Perform inclusion configuration in test1/urls.py , create the corresponding urls.py in each application, and perform specific configurations in the urls.py file under each application.

Define the urlpartterns list and store the url() object. The name of this list is fixed.

2. The syntax of url definition

url() object is defined in the django.conf.urls package and consists of two syntax structures

(1), Syntax 1 : Contain, include the urls.py of other applications in the urls.py under the project folder with the same name

Create a urls.py file in the custom application to define url(), and then add the urls.py The custom urls.py is introduced in the urls.py under the folder. The purpose of this is to configure urls.py inside the application, so that the data is clearer and easier to maintain.

Introduce the syntax of booktest/urls.py into test1/urls.py

url(r'^',include('应用名称.urls')),
# 此处的urls指的是各自应用（booktest）中urls.py文件的名称，如果是urls.py，即为urls

(2), Syntax 2: Definition, specify the corresponding relationship between URL and view function

Create urls.py inside the respective applications and specify the corresponding relationship between the request address and the view. The format is as follows:

url(正则,'视图函数名称')

Example:

Create the url of the homepage in booktest/urls.py:

from django.conf.urls import url
from booktest import views
urlpatterns=[
    url(r'^$',views.index),
]

Note: It is recommended to use r in the regular part, which means that the string is not escaped, so you only need to write one \ in the regular expression. You cannot add a backslash at the beginning. It is recommended to add a backslash at the end, because the browser's URL is the same with or without adding \ at the end.

3. Obtain the parameter value carried in the url

The requested url is regarded as an ordinary python string and matches request parameters that do not include domain name, get or post, such as: The request address is as follows:

http://localhost:8080/detail/1?a=10

Among the above request addresses, the only strings that match the regular expression in the url() function are:

detail/

If you want to carry RESTFUL style parameters in the requested url, you need to use grouping in the regular expression of the url() function, that is, use the () sign, which is divided into: Positional parameters, keyword parameters.

Note: Do not mix the two parameter methods. Only one parameter method can be used in a regular expression.

(1) Positional parameters

Use the () sign directly and pass it to the view through the positional parameters

The regular expression in the url() function is written as:# The corresponding function writing in ##

url(r'^detail(\d+)/$',views.show_books),

views.py is:

def show_books(request, id):    # 此处获取的id为1
    return HttpResponse('show_books')

(2), keyword parameters

If keyword parameters are used, the regular expression in the url() function The expression grouping is to name each group

. For example, the accessed url is: http://localhost:8000/delete/1?a=10

The regular expression of the url() function The expression is written as:

url(r&#39;^delete(?P<id1>\d+)/$&#39;,views.show_book),

The function in views.py is written as:

def show_arg(request,id1):
    return HttpResponse('show %s'%id1)

Note: If keyword parameters are used, Then the parameter name of the corresponding function in views.py must be consistent with the name of the group in the regular expression, otherwise an error will be reported. 2. View

1. What is a view

A view is a function in python. Views are generally defined in the "application/views.py" file, which is this file. Example "booktest/views.py".

The view must return an HttpResponse object or sub-object as a response. The response can be the HTML content of a web page, a redirect function, or a 404 error, etc.

The first parameter of the view must be an HttpRequest object. Other parameters may also include: keyword parameters or positional parameters (either one of the two)

                                                                         Built-in error view

(1), built-in error view

Django has built-in views for handling HTTP errors. The main errors and views include:

404: page not found View

          500: server error View

If you want to see the error view instead of debugging information, you need to modify the DEBUG item configuration information in the "test/settings.py" file

（2）、404错误及视图

        将请求地址进行url匹配之后，没有找到匹配的正则表达式，则调用404视图，这个视图会调用404.html模版进行渲染，视图传递变量request_path给模版，表示导致错误的URL。

在templates中创建404.html

<html>
<head>
    <title></title>
</head>
<body>
找不到了
<hr/>
{{request_path}}
</body>
</html>

在浏览器中输入如下网址：

http://localhost:8000/test/

运行效果如下：

（3）、500错误及视图

        在视图中代码运行报错将会发生500错误，调用内置错误视图，使用templates/500.html模版进行渲染。

三、HttpRequest对象

1、HttpRequest对象

        服务器接收到HTTP请求后，会根据报文创建HttpRequest对象，这个对象不需要我们手动创建，直接使用服务器构建好的对象即可。视图函数中的第一个参数必须是HttpRequest对象，该对象类定义在django.http模块中。

2、属性

        path：一个字符串，表示请求的页面的完整路径，不包含域名和参数部分。

        method：一个字符串，表示请求使用的HTTP方法，常用值包括：'GET'、'POST'。

                在浏览器中给出地址发出请求采用get方式，如超链接。

                

                在浏览器中点击表单的提交按钮发起请求，如果表单的method设置为post则为post请求。

        encoding：一个字符串，表示提交的数据的编码方式。

                如果为None则表示使用浏览器的默认设置，一般为utf-8。

                这个属性是可写的，可以通过修改它来修改访问表单数据使用的编码，接下来对属性的任何访问将使用新的encoding值。

        GET：QueryDict类型对象，类似于字典，包含get请求方式的所有参数。

        POST：QueryDict类型对象，类似于字典，包含post请求方式的所有参数。

        FILES：一个类似于字典的对象，包含所有的上传文件。

        COOKIES：一个标准的Python字典，包含所有的cookie，键和值都为字符串。

        session：一个既可读又可写的类似于字典的对象，表示当前的会话，只有当Django 启用会话的支持时才可用，详细内容见"状态保持"。

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