Python基础 - Model - 《Python项目以及容器化技术》

创建项目以及配置虚拟环境
为项目文件创建数据库及数据库用户
*_修改_settings.py文件*
Model
- 6.2多表继承

配置文件存放位置

/etc/mysql/mysql.conf.d/mysqld.cnf

创建项目以及配置虚拟环境

安装创建虚拟环境的工具

sudo apt install python3-venv

创建合适的文件夹保存项目文件

cd ~/桌面
mkdir django_venv

创建虚拟环境

python3 -m venv bbs_python38

进入项目文件

cd /django_env

激活环境

source ./bin/activate

安装指定版本的django

pip install django==2.7.0

通过IDE查看是否安装成功不退出环境，当前工作目录

python3
import django
django.get_version()

为项目文件创建数据库及数据库用户

以root用户登录数据库

mysql -u root -p

创建数据库

create database django_bbs;

查看数据库

show databases;

创建用户(前为用户后为密码)

create user work identified by ‘django_bbs’;

添加权限

grant all on django_bbs.* to ‘work’@’%’ with grant option;

退出数据库并且以指定身份登录

mysql -u work -p django_bbs

安装创建项目的文件

sudo apt install python-django-common

创建项目(在指定工作路径)

django-admin startproject my_bbs

启动项目

python manage.py runserver

_修改_settings.py文件

LANGUAGE_CODE = 'zh-Hans'TIME_ZONE = 'UTC' USE_I18N = TrueUSE_L10N = TrueUSE_TZ = True

修改默认数据库

原有数据

DATABASES = {  'default': {    'ENGINE': 'django.db.backends.sqlite3',    'NAME': os.path.join(BASE_DIR, 'db.sqlite3'),  }}

修改之后的

DATABASES = {  'default': {    'ENGINE': 'django.db.backends.mysql',    'NAME': 'django_bbs',        'USER': 'work',        'PASSWORD': 'django_bbs',        'HOST': '127.0.0.1',        'PORT': '3306',  }}

安装pymysql

解决安装mysqlclient失败的问题

sudo apt install -y mysql-clientsudo apt-get install libmysqlclient-devsudo apt install libssl-devsudo apt install libcrypto++-devpip3 install mysqlclient

安装成功

迁移数据库

cd ~/桌面/django_venv/bbs_python38/my_bbspython manage.py makemigrationspython manage.py migrate

查看迁移文件

登录数据库

show databases;use django_bbs;show tables;

创建超级管理员

python manage.py createsuperuser --username=admin --email=admin@email.com

user : adminpassword:le930067

创建app

python manage.py startapp post

生成项目包版本信息表

pip freeze > requirements.txt

查看版本信息

gedit requirements.txt

常用命令

python manage.py shell

可以快速进入python 命令行

post — app中的项目构建

from django.db import modelsfrom django.contrib.auth.models import User# Create your models here.class BaseModel(models.Model):    """    base_model of project post    """    class Metal:        abstract = True        ordering = ['created_time']    created_time = models.DateTimeField(auto_now_add=True, help_text=u'time of creation')  #     last_modified = models.DateTimeField(auto_now_add=True, help_text='time of creation')    def __str__(self):        raise NotImplementedErrorclass Topic(BaseModel):    """    topics of BBS    """    title = models.CharField(max_length=255, unique=True, help_text='label of topics')    content = models.TextField(help_text=u'content of topics')    is_online = models.BooleanField(default=True, help_text='whether topics is online')    user = models.ForeignKey(to=User, to_field='id', on_delete=models.CASCADE, help_text='tables of association')    def __str__(self):        return '%d : %s' % (self.id, self.title[0:20])class Comment(BaseModel):    """    comment of topics    """    content = models.CharField(max_length=255, help_text='comment of topics')    topic = models.ForeignKey(to=Topic, to_field='id', on_delete=models.CASCADE, help_text=u'table of association topic')    up = models.IntegerField(default=0, help_text=u'agree')    down = models.IntegerField(default=0, help_text=u'disagree')    def __str__(self):        return '%d : %s' % (self.id, self.content[0:20])

给项目文件注册app（第一行）

INSTALLED_APPS = [    'post.apps.PostConfig',    'django.contrib.admin',    'django.contrib.auth',    'django.contrib.contenttypes',    'django.contrib.sessions',    'django.contrib.messages',    'django.contrib.staticfiles',]

打印迁移文件

python manage.py sqlmigrate post 0001

迁移文件代码展示

BEGIN;---- Create model BaseModel--CREATE TABLE `post_basemodel` (`id` integer AUTO_INCREMENT NOT NULL PRIMARY KEY, `created_time` datetime(6) NOT NULL, `last_modified` datetime(6) NOT NULL);---- Create model Comment--CREATE TABLE `post_comment` (`basemodel_ptr_id` integer NOT NULL PRIMARY KEY, `content` varchar(255) NOT NULL, `up` integer NOT NULL, `down` integer NOT NULL);---- Create model Topic_Many--CREATE TABLE `post_topic_many` (`basemodel_ptr_id` integer NOT NULL PRIMARY KEY, `title` varchar(255) NOT NULL UNIQUE, `content` longtext NOT NULL, `is_online` bool NOT NULL, `user_id` integer NOT NULL);---- Add field topic to comment--ALTER TABLE `post_comment` ADD COLUMN `topic_id` integer NOT NULL;ALTER TABLE `post_comment` ADD CONSTRAINT `post_comment_basemodel_ptr_id_27053bac_fk_post_basemodel_id` FOREIGN KEY (`basemodel_ptr_id`) REFERENCES `post_basemodel` (`id`);ALTER TABLE `post_topic_many` ADD CONSTRAINT `post_topic_many_basemodel_ptr_id_0e9c4bdc_fk_post_basemodel_id` FOREIGN KEY (`basemodel_ptr_id`) REFERENCES `post_basemodel` (`id`);ALTER TABLE `post_topic_many` ADD CONSTRAINT `post_topic_many_user_id_ae7619c5_fk_auth_user_id` FOREIGN KEY (`user_id`) REFERENCES `auth_user` (`id`);ALTER TABLE `post_comment` ADD CONSTRAINT `post_comment_topic_id_de2ae665_fk_post_basemodel_id` FOREIGN KEY (`topic_id`) REFERENCES `post_basemodel` (`id`);COMMIT;

检查错误命令

python manage.py check

执行迁移命令

python manage.py migrate

迁移效果

Model - 图1

Model

6.2多表继承

  # 该字段用来说明多表继承，从SQL生成语句查询可知，django会自动为其添加主键和指向的表格class CategoryTopic(Topic_Many):    """    分类topic    """    category = models.CharField(max_length=32, help_text='类别')

Model模块全字段代码

from django.db import models
from django.contrib.auth.models import User
# Create your models here.
class BaseModel(models.Model):  # 直接继承自基类
    """
    post应用中的Model类
    """
    class Meta:
        abstract = True  # 声明这个是个抽象类，无法被实例化，也不会创建数据表
        ordering = ['-created_time']  # 排序规则， 按照创建时间逆序排列 先后排序则为['-created_time, last+modified']
    created_time = models.DateTimeField(auto_now_add=True, help_text=u'创建时间')  # 时间域继承自Model,自动将创建时间锚定为当前时间
    last_modified = models.DateTimeField(auto_now_add=True, help_text='修改时间')  # 时间域继承自Model，自动将修改时间锚定为当前时间
    def __str__(self):  # 打印Model实例的样式
        raise NotImplementedError
class SignField(models.CharField):
    """
    签名 Filed
    """
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)  # 需要从其他字段继承，且签名的长度不一
    def get_prep_value(self, value):
        return "<my_bbs> %s" % value  # 从数据库数据表中读取什么数据？特别注意，返回值会作为数据存储到数据表中，所以签名也会被报错到数据表中
class Topic_Many(BaseModel):  # 直接继承自基类
    """
    BBS论坛发布的话题
    """
    title = SignField(max_length=255, unique=True, help_text='话题标题')  # 类似于超话可以从人衍生
    content = models.TextField(help_text=u'话题内容')
    is_online = models.BooleanField(default=True, help_text='话题是否在线')
    # user为topic_many的外键，被其引用
    user = models.ForeignKey(to=User, to_field='id', on_delete=models.CASCADE, help_text='关联用户表')
    unique_together = (('title', 'is_online'), ('title', 'content'))  # 联合索引，元组双元素，父子级别
  # 测试index参数，这个参数是用来制作索引的
    indexes = {
        models.Index(fields=['title']),  # 指定索引的字段
        models.Index(fields=['title', 'is_online'], name='title_is_online_idx')
    }
    permissions = (
        ("can_read_topic", "可以阅读话题"),
        ("can_discuss_topic", "可以评论话题")
    )
    def default_title(self):
        return 'default title'
    def __str__(self):
        return '%d: %s' % (self.id, self.title[0:20])
  # 该字段用来说明多表继承，从SQL生成语句查询可知，django会自动为其添加主键和指向的表格
class CategoryTopic(Topic_Many):
    """
    分类topic
    """
    category = models.CharField(max_length=32, help_text='类别')
  # 基类的代理模型：创建方法，功能：返回逻辑上不同的排序，理论意义在于：不修改基类原始定义，但对代理的增删改差会同步到基类
  # 同时代理模型只能继承自一个非抽象的基类，且不能同时继承多个
class ProxyTopic_Many(Topic_Many):
    """代理Topic
    """
    class Meta:
        ordering = ['id']
        proxy = True
    def is_topic_many_valid(self):
        return 'django' in self.title
class Comment(BaseModel):
    """
    BBS话题的评论
    """
    content = models.CharField(max_length=255, help_text='话题评论')
    topic = models.ForeignKey(to='Topic_Many', to_field='id', on_delete=models.CASCADE, help_text=u'关联话题表')
    up = models.IntegerField(default=0, help_text=u'支持')
    down = models.IntegerField(default=0, help_text=u'反对')
    def __str__(self):
        return '%d: %s' % (self.id, self.content[0:20])
class People(models.Model):  # 通用字段，用于用户选择双元组，定义在Model内部，是基类么？
    MALE = 'm'
    FEMALE = 'f'
    GENDER_CHOICE = (
        (MALE, '男性'),
        (FEMALE, '女性')
    )
    gender = models.CharField(max_length=1, choices=GENDER_CHOICE, default=MALE)

项目settings文件

"""
Django settings for my_bbs project.
Generated by 'django-admin startproject' using Django 2.0.7.
For more information on this file, see
https://docs.djangoproject.com/en/2.0/topics/settings/
For the full list of settings and their values, see
https://docs.djangoproject.com/en/2.0/ref/settings/
"""
import os
# Build paths inside the project like this: os.path.join(BASE_DIR, ...)
BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
# Quick-start development settings - unsuitable for production
# See https://docs.djangoproject.com/en/2.0/howto/deployment/checklist/
# SECURITY WARNING: keep the secret key used in production secret!
SECRET_KEY = '^=qr$i13wl6beju-_o10ntei9za+3n5q7om+6^_s4@z+8j5@*1'
# SECURITY WARNING: don't run with debug turned on in production!
DEBUG = True
ALLOWED_HOSTS = []
# Application definition
INSTALLED_APPS = [
    'post.apps.PostConfig',
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
]
MIDDLEWARE = [
    'django.middleware.security.SecurityMiddleware',
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.middleware.common.CommonMiddleware',
    'django.middleware.csrf.CsrfViewMiddleware',
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django.contrib.messages.middleware.MessageMiddleware',
    'django.middleware.clickjacking.XFrameOptionsMiddleware',
]
ROOT_URLCONF = 'my_bbs.urls'
TEMPLATES = [
    {
        'BACKEND': 'django.template.backends.django.DjangoTemplates',
        'DIRS': [],
        'APP_DIRS': True,
        'OPTIONS': {
            'context_processors': [
                'django.template.context_processors.debug',
                'django.template.context_processors.request',
                'django.contrib.auth.context_processors.auth',
                'django.contrib.messages.context_processors.messages',
            ],
        },
    },
]
WSGI_APPLICATION = 'my_bbs.wsgi.application'
# Database
# https://docs.djangoproject.com/en/2.0/ref/settings/#databases
DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.mysql',
        'NAME': 'django_bbs',
    'USER': 'work',
    'PASSWORD': 'django_bbs',
    'HOST': '127.0.0.1',
    'PORT': '3306',
    }
}
# Password validation
# https://docs.djangoproject.com/en/2.0/ref/settings/#auth-password-validators
AUTH_PASSWORD_VALIDATORS = [
    {
        'NAME': 'django.contrib.auth.password_validation.UserAttributeSimilarityValidator',
    },
    {
        'NAME': 'django.contrib.auth.password_validation.MinimumLengthValidator',
    },
    {
        'NAME': 'django.contrib.auth.password_validation.CommonPasswordValidator',
    },
    {
        'NAME': 'django.contrib.auth.password_validation.NumericPasswordValidator',
    },
]
# Internationalization
# https://docs.djangoproject.com/en/2.0/topics/i18n/
LANGUAGE_CODE = 'zh-Hans'
TIME_ZONE = 'UTC'
USE_I18N = True
USE_L10N = True
USE_TZ = False
# Static files (CSS, JavaScript, Images)
# https://docs.djangoproject.com/en/2.0/howto/static-files/
STATIC_URL = '/static/'

Model

创建项目以及配置虚拟环境

为项目文件创建数据库及数据库用户

*_修改_settings.py文件*

Model

6.2多表继承

_修改_settings.py文件