欢迎您访问程序员文章站本站旨在为大家提供分享程序员计算机编程知识!
您现在的位置是: 首页  >  后端开发

编写Python的web框架中的Model的教程

程序员文章站 2022-04-29 15:43:13
...
有了ORM,我们就可以把Web App需要的3个表用Model表示出来:

import time, uuid

from transwarp.db import next_id
from transwarp.orm import Model, StringField, BooleanField, FloatField, TextField

class User(Model):
  __table__ = 'users'

  id = StringField(primary_key=True, default=next_id, ddl='varchar(50)')
  email = StringField(updatable=False, ddl='varchar(50)')
  password = StringField(ddl='varchar(50)')
  admin = BooleanField()
  name = StringField(ddl='varchar(50)')
  image = StringField(ddl='varchar(500)')
  created_at = FloatField(updatable=False, default=time.time)

class Blog(Model):
  __table__ = 'blogs'

  id = StringField(primary_key=True, default=next_id, ddl='varchar(50)')
  user_id = StringField(updatable=False, ddl='varchar(50)')
  user_name = StringField(ddl='varchar(50)')
  user_image = StringField(ddl='varchar(500)')
  name = StringField(ddl='varchar(50)')
  summary = StringField(ddl='varchar(200)')
  content = TextField()
  created_at = FloatField(updatable=False, default=time.time)

class Comment(Model):
  __table__ = 'comments'

  id = StringField(primary_key=True, default=next_id, ddl='varchar(50)')
  blog_id = StringField(updatable=False, ddl='varchar(50)')
  user_id = StringField(updatable=False, ddl='varchar(50)')
  user_name = StringField(ddl='varchar(50)')
  user_image = StringField(ddl='varchar(500)')
  content = TextField()
  created_at = FloatField(updatable=False, default=time.time)

在编写ORM时,给一个Field增加一个default参数可以让ORM自己填入缺省值,非常方便。并且,缺省值可以作为函数对象传入,在调用insert()时自动计算。

例如,主键id的缺省值是函数next_id,创建时间created_at的缺省值是函数time.time,可以自动设置当前日期和时间。

日期和时间用float类型存储在数据库中,而不是datetime类型,这么做的好处是不必关心数据库的时区以及时区转换问题,排序非常简单,显示的时候,只需要做一个float到str的转换,也非常容易。
初始化数据库表

如果表的数量很少,可以手写创建表的SQL脚本:

-- schema.sql

drop database if exists awesome;

create database awesome;

use awesome;

grant select, insert, update, delete on awesome.* to 'www-data'@'localhost' identified by 'www-data';

create table users (
  `id` varchar(50) not null,
  `email` varchar(50) not null,
  `password` varchar(50) not null,
  `admin` bool not null,
  `name` varchar(50) not null,
  `image` varchar(500) not null,
  `created_at` real not null,
  unique key `idx_email` (`email`),
  key `idx_created_at` (`created_at`),
  primary key (`id`)
) engine=innodb default charset=utf8;

create table blogs (
  `id` varchar(50) not null,
  `user_id` varchar(50) not null,
  `user_name` varchar(50) not null,
  `user_image` varchar(500) not null,
  `name` varchar(50) not null,
  `summary` varchar(200) not null,
  `content` mediumtext not null,
  `created_at` real not null,
  key `idx_created_at` (`created_at`),
  primary key (`id`)
) engine=innodb default charset=utf8;

create table comments (
  `id` varchar(50) not null,
  `blog_id` varchar(50) not null,
  `user_id` varchar(50) not null,
  `user_name` varchar(50) not null,
  `user_image` varchar(500) not null,
  `content` mediumtext not null,
  `created_at` real not null,
  key `idx_created_at` (`created_at`),
  primary key (`id`)
) engine=innodb default charset=utf8;

如果表的数量很多,可以从Model对象直接通过脚本自动生成SQL脚本,使用更简单。

把SQL脚本放到MySQL命令行里执行:

$ mysql -u root -p 

我们就完成了数据库表的初始化。
编写数据访问代码

接下来,就可以真正开始编写代码操作对象了。比如,对于User对象,我们就可以做如下操作:

# test_db.py

from models import User, Blog, Comment

from transwarp import db

db.create_engine(user='www-data', password='www-data', database='awesome')

u = User(name='Test', email='test@example.com', password='1234567890', image='about:blank')

u.insert()

print 'new user id:', u.id

u1 = User.find_first('where email=?', 'test@example.com')
print 'find user\'s name:', u1.name

u1.delete()

u2 = User.find_first('where email=?', 'test@example.com')
print 'find user:', u2

可以在MySQL客户端命令行查询,看看数据是不是正常存储到MySQL里面了。

相关标签: Python