Python 网站开发(4) -- 编写Model
编写Model
orm.py编写完成后，就可以把网站应用需要的三个表（user, blog, comment）用Model表示出来。在www目录下，新建models.py:
import time, uuid
from orm import Model, StringField, BooleanField, FloatField, TextField
def next_id():
return '%015d%s000' % (int(time.time() * 1000), uuid.uuid4().hex)
class User(Model):
__table__ = 'users'
id = StringField(primary_key=True, default=next_id, ddl='varchar(50)')
email = StringField(ddl='varchar(50)')
passwd = StringField(ddl='varchar(50)')
admin = BooleanField()
name = StringField(ddl='varchar(50)')
image = StringField(ddl='varchar(500)')
created_at = FloatField(default=time.time)
class Blog(Model):
__table__ = 'blogs'
id = StringField(primary_key=True, default=next_id, ddl='varchar(50)')
user_id = StringField(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(default=time.time)
class Comment(Model):
__table__ = 'comments'
id = StringField(primary_key=True, default=next_id, ddl='varchar(50)')
blog_id = StringField(ddl='varchar(50)')
user_id = StringField(ddl='varchar(50)')
user_name = StringField(ddl='varchar(50)')
user_image = StringField(ddl='varchar(500)')
content = TextField()
created_at = FloatField(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save()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
由于网站表的数量较少，可以手动创建SQL脚本schema.sql到根目录：
-- schema.sql
drop database if exists awesome;
drop user if exists 'www-data'@'localhost';
create database awesome;
use awesome;
create user 'www-data'@'localhost' identified by 'www-data';
alter user 'www-data'@'localhost' identified with mysql_native_password by 'www-data';
grant select, insert, update, delete on awesome.* to 'www-data'@'localhost';
create table users (
`id` varchar(50) not null,
`email` varchar(50) not null,
`passwd` 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;
把SQL脚本 schema.sql放到MySQL命令行里执行，就完成了数据库表的初始化：
$ mysql -u root -p < schema.sql
然后我们可以编写数据访问代码test.py测试一下。如新建一个User的对象：
import orm
import asyncio
from models import User, Blog, Comment
async def test(loop):
await orm.create_pool(loop=loop, user='root', password='root', db='awesome')
u = User(name='Test', email='test@qq.com', passwd='1234567890', image='about:blank')
await u.save()
## 网友指出添加到数据库后需要关闭连接池，否则会报错 RuntimeError: Event loop is closed
orm.__pool.close()
await orm.__pool.wait_closed()
if __name__ == '__main__':
loop = asyncio.get_event_loop()
loop.run_until_complete(test(loop))
loop.close()
运行test.py后，可以在MySQL客户端命令行查询，看看测试的数据是不是正常储存到MySQL里面。
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