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This article mainly talks about "Learning and using the basic knowledge of Django". Friends who are interested may wish to have a look. The method introduced in this paper is simple, fast and practical. Let's let the editor take you to learn the basics of Django.

I. the classification of web framework and the use of wsgiref modules introduce the nature of web framework.

Communication between socket server and browser

Socket server function division:

Responsible for sending and receiving messages with browsers (socket communication)-- > wsgiref/uWsgi/gunicorn...

According to the user to access different paths to execute different functions c. Read out the content from HTML and replace the string-- > jinja2 (template language)

Classification of Web frameworks in Python:

Divided by the above three functions:

The framework comes with a _ c-- > Tornado.

The framework comes with b and c, using third-party a-> Django

The framework comes with b, using third-party an and c-> Flask

Divided by another dimension:

Django-- > large and comprehensive (it has everything you can use to make a website)

Other-- > Flask lightweight

2. Django installation and creation project installation Djangopip3 install django== version number (1.11.11plus 2.2.6) pip3 install-I https://pypi.tuna.tsinghua.edu.cn/simple/ django== version number (1.11.11plus 2.2.6) command line create project django-admin startproject project name pycharm create project File-- > New project-- > left select Django-- > right fill in the project path to set the Django project:

Manage.py: project management portal file

Settings.py:

1. Configure the location where the HTML file is stored Templates (the configuration for storing the HTML file) start the python3 manage.py runserver port on the specified IP and port-- > start python3 manage.py runserver on the specified port-- > start it on port 8000 of this machine by default

PyCharm start

Click the green triangle, you can directly start the Django project (as long as the left side of the triangle is your Django project name) Django WEB request process (simplified version)

Start the Django project and wait for the user to connect

The browser enters URL in the address bar to connect to my Django project

Find the corresponding relationship between path and function in urls.py

Execute the corresponding function

Return response

What is APP in Django? what is APP? And why use APP?

It is convenient for us to manage and implement different business functions in a large Django project.

Project-- > Project (University) APP-- > commands for applications (Linux College / Python College / big data College / Java College) to create APP

Command line, enter: python3 manage.py startapp app name in the root directory of the Django project

IV. Urls.py routing

Request without parameters

Path ('admin/', admin.site.urls)

Request with parameters

Path ('solution//', views.ListSolution.as_view (), name= "solutionList"), V. Views.py view

Specifically used to define functions that handle requests

Basic three-piece set of from django.shortcuts import HttpResponse, render, redirect

HttpResponse ("content to be returned")-- > is usually used to return data directly

Render (request, "html file", {"K1": V1})-- > return a HTML file or open a file for string substitution

Redirect ("URL")-- > tell the user's browser to access other URL

Request correlation

GET request and POST request

GET request: 1. The browser requests a page 2. When search engines search keywords, 3. A tag POST request: 1. The browser submits data to the server, such as login / registration, etc. Modify (add) large chunks of data 3. Upload files

GET requests URL to pass a value

127.0.0.1:8000/user/? Variable name = variable value

Get the method of request request

Request.method = = "GET" / "POST"

Get GET request parameters

Request.GET.get (variable name, default)

Get POST request parameters

Request.POST.get (variable name of name, default value) # get a single value request.POST.getlist (variable name of name) # get multi-choice list value VI. ORM model (Model) ORM corresponding relation class-- > data table object-- > data row attribute-- > what field ORM can do.

Manipulate data tables-- > create / delete / modify tables (manipulate classes in models.py)

Operation of data rows-- > addition, deletion, modification and query of data

Detailed steps to connect to MySQL using Django's ORM:

Create your own database: create database database name

Set the configuration for connecting to the database in the Django project (settings.py tells Django which database to connect to)

# database-related configuration DATABASES = {'default': {' ENGINE': 'django.db.backends.mysql', # database type of connection' HOST': '127.0.0.1, # address of connection database' PORT': 3306, # port 'NAME': "day61" # Database name 'USER':' root', # user 'PASSWORD':' 123456' # password}}

Define a class in the models.py file under app that must inherit models.Model

Class class name (models.Model):...

Execute two commands

Python3 manage.py makemigrations # New Model or Model changes need to execute python3 manage.py migrate # translate the changes into SQL statements, go to the database to execute a simple Model example of defining classes in app/models.py: # Publishing class Publisher (models.Model): id = models.AutoField (primary_key=True) # self-added ID primary key # create a varchar (64) unique non-empty field name = models.CharField (max_length=64 Null=False, unique=True) the addition and query of ORM single table

Query

Models.UserInfo.objects.all () # query all

Increase

Models.UserInfo.objects.create (field name = field value)

Delete

Solution = Solution.objects.get (id=id) # get the object solution.delete () # and then delete # or Solution.objects.get (id=id) .delete ()

Modify

Solution = Solution.objects.get (id=id) # get the object solution first. Field name = field value # modify the value of a field solution.save () # Save and modify one-to-many, many-to-many model

Relationship:

1. There can only be one publisher for a book. A book can have more than one author. One author can write multiple books: one-to-many publishers and books: one-to-many-- > Foreign key books and authors: many-to-many-- > relate with the third table

One-to-many relational operation

# Publishing class Publisher (models.Model): id = models.AutoField (primary_key=True) # self-added ID primary key # create a unique non-empty field for varchar (64) name = models.CharField (max_length=64, null=False) Unique=True) addr = models.CharField (max_length=128) # Book class Book (models.Model): id = models.AutoField (primary_key=True) # self-added ID primary key # create a unique non-empty field of varchar (64) title = models.CharField (max_length=64, null=False) Unique=True) # and the foreign key field associated with the publisher publisher= models.ForeignKey (to= "Publisher") # add new_book_obj = models.Book.objects.create (title= "name of the new book", # publisher=publusher_obj, publisher_id=7) # modify book_obj = models.Book.objects.get (id=9) book_obj.title=request.POST.get ("book_title") book_obj.publisher_id=9book_obj.save ()

Many-to-many relational operation

# author table class Author (models.Model): id = models.AutoField (primary_key=True) name = models.CharField (max_length=16, null=False, unique=True) # tell ORM that there is a many-to-many relationship between this table and book table ORM automatically generates the third table for me book = models.ManyToManyField (to= "Book") def _ _ str__ (self): return "" .format (self.name) # add # fetch the submitted data new_author_name = request.POST.get ("author_name") # post must use getlist when the data submitted is multiple values Such as multi-selected checkbox and multi-selected selectbooks = request.POST.getlist ("books") # create author new_author_obj = models.Author.objects.create (name=new_author_name) # to establish a corresponding relationship between a new author and a book Automatically submit new_author_obj.book.set (books) Template template value {{variable name}} Loop {% for user in user_list%}... {% endfor%} Loop count {{forloop.counter}} Last cycle {{forloop.last}} judge {% if book_obj.publisher_id = = publisher.id%} {# the publisher associated with the current book selects #} {{publisher.name}} by default % else%} {# other publishers do not check #} {{publisher.name}} {% endif%} {# if the current book is in all the books associated with the current author #} {% if book in author.book.all%} {{book.title} {% else%} {{book.title}} {% endif%} here I believe you have a deeper understanding of "learning and using the basic knowledge of Django". You might as well do it in practice. Here is the website, more related content can enter the relevant channels to inquire, follow us, continue to learn!

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