在《peewee用法考察》中，我初步掌握peewee的一些常用操作。而做这些准备，是为了在tornado中使用。
tornado是一个异步网络IO非阻塞框架，这意味着涉及到IO阻塞操作，我们都应该以异步的形式去进行。而peewee本身并不是异步的，因此我们还需要引入另外一些库才能更好的契合tornado。
>>> 阅读原文获得最佳体验-yuchanns'Atelier
我们需要什么类库
- peewee-async
- aiomysql
peewee-async是一个基于asyncio的封装成的库，用于进行peewee异步操作。而peewee是基于pymysql进行操作的，pymysql异步操作mysql则需要aiomysql库的支持。
注意：目前支持tornado3.0+的peewee-async属于预发行版本，需要添加-pre参数下载。
Version 0.6.0a is published as pre-release, mind the "a" in version identifier. That means in order to install it you should specify --pre flag for pip.
pip install -pre peewee-async
pip install aiomysql
与tornado结合：同步阻塞下的情况
# -*- coding: utf-8 -*-
from tornado.web import Application, RequestHandler
from tornado.httpserver import HTTPServer
from tornado.ioloop import IOLoop
from models import *
import sys
class MainHandler(RequestHandler):
def get(self):
uid = self.get_argument('uid', 10000)
query = User.select(User.uname).where(User.uid == uid).get()
self.write('uname:%s' % query.uname)
class TestHandler(RequestHandler):
def get(self):
self.write('test here')
def main():
app = Application([
(r'/', MainHandler),
(r'/test', TestHandler),
])
try:
server = HTTPServer(app)
server.listen(8000)
IOLoop.current().start()
except KeyboardInterrupt:
print('Exit')
if __name__ == '__main__':
sys.exit(main())
启动mysql交互界面，锁住user表的读写操作，模拟硬盘IO阻塞。
use peewee;
lock table user write;
然后先后访问localhost:8000/和localhost:8000/test，我们会发现两个访问都阻塞在请求状态，直到我们进行
unlock table;
解锁写锁之后才能获得数据。
与tornado结合：异步硬盘IO非阻塞下的情况
为了使用peewee-async，首先我们需要对models.py文件一点修改：
# -*- coding: utf-8 -*-
from peewee import *
"""引入peewee_async相关类库"""
from peewee_async import MySQLDatabase as AsyncMySQLDatabase, Manager
# database = MySQLDatabase('peewee', **{'charset': 'utf8', 'use_unicode': True, 'host': 'localhost', 'port': 3306, 'user': 'root', 'password': ''})
"""将数据库连接改成peewee_async.MySQLDatabase"""
database = AsyncMySQLDatabase('peewee', **{'charset': 'utf8', 'use_unicode': True, 'host': 'localhost', 'port': 3306, 'user': 'root', 'password': '87260333as'})
class UnknownField(object):
def __init__(self, *_, **__): pass
class BaseModel(Model):
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
"""将事务改成atomic_async"""
self.trans = database.atomic_async
"""添加一个Manager类"""
self.object = Manager(database)
class Meta:
database = database
# 下略……
peewee-async官方文档写得很简略，使用方法也不难，只是在peewee原有的基础上多加了一点嵌套操作。
比如，查询操作：（其中async/await是python3.5+异步操作的新特性，若不明白请自行查阅官方文档）
class MainHandler(RequestHandler):
"""使用async关键字标识异步操作"""
async def get(self):
user = User()
uname = self.get_argument('uname', 'j')
uid = self.get_argument('uid', 10002)
try:
"""使用await关键字等待阻塞操作"""
"""单条查询使用object.get()方法将原本的peewee操作包裹起来"""
row = await user.object.get(
User.select(User.uname).where(User.uid == uid)
)
"""多条查询"""
query = await user.object.execute(
User.select(User.uname).where(User.uname.startswith(uname))
)
except User.DoesNotExist:
"""当查不到数据的时候会抛出DoesNotExist错误"""
self.write('查无数据')
else:
self.write('row uname: %s and query unames:%s' % (row.uname, ', '.join([row.uname for row in query])))
启动进程，当我们再次锁住user表写锁，然后先后访问localhost:8000/和localhost:8000/test，就会发现，虽然第一个请求还在阻塞状态，第二个请求却已经成功看到屏幕上打印出来的"test here"文字。而当我们解锁user表之后，第一个请求也能顺利完成。
其余常规操作
插入/更新数据
async def post():
"""md5加密密码"""
m = hashlib.md5()
m.update('123456'.encode())
pwd = m.hexdigest()
"""头像"""
avartar = 'https://avatars2.githubusercontent.com/u/25029451'
user = User()
data_source = [
(avartar, 'Doreis', pwd),
(avartar, 'Dorein', pwd),
(avartar, 'Doreiv', pwd),
]
field = (User.avartar, User.uname, User.password)
try:
"""插入多条数据"""
await user.object.execute(
User.insert_many(data_source, field)
)
result = await user.object.get(User.select(User.uid, User.integral).where(User.uname == 'Doreis'))
"""使用async关键字开启事务"""
async with user.trans():
"""更新数据"""
await user.object.execute(User.update(
integral=result.integral+100
).where(User.uid == result.uid))
"""插入单条数据"""
await user.object.execute(Integral.insert(
uid=result.uid,
change=100,
total=result.integral + 100
))
self.write('insert complete')
except Exception as e:
print(repr(e))
self.write('insert failed')
jion查询
async def get(self):
user = User()
try:
"""join查询"""
query_join = await user.object.execute(
Balance.select(
User.uname, Balance.change,
Balance.total, Balance.addtime
).join(
User, JOIN.RIGHT_OUTER,
on=(Balance.uid == User.uid)
).where(
Balance.uid == 10012
).order_by(-Balance.addtime)
)
for row_join in query_join:
print('%s:%.2f:%.2f:%s' % (
row_join.user.uname, row_join.change,
row_join.total, row_join.addtime
))
except User.DoesNotExist:
"""当查不到数据的时候会抛出DoesNotExist错误"""
self.write('查无数据')
else:
self.write('query unames:%s' % (row.uname, ', '.join([row.uname for row in query])))
union查询
关于union操作，peewee_async原本并不支持。我开了个issue询问了作者，作者表示做出一些修改就可以支持。
Not sure if
select()coroutine could handle that but you can try itpeewee_async.select(union_query))
If it works, then we can just add handlingModelCompoundSelectQuerytoexecute()viaselect()
所以，首先，我们对peewee_async库的源文件peewee_async.py中的
execute()做出一点修改：
async def execute(query):
"""Execute *SELECT*, *INSERT*, *UPDATE* or *DELETE* query asyncronously.
:param query: peewee query instance created with ``Model.select()``,
``Model.update()`` etc.
:return: result depends on query type, it's the same as for sync
``query.execute()``
"""
"""在这里，添加ModelCompoundSelectQuery类"""
if isinstance(query, (peewee.Select, peewee.ModelCompoundSelectQuery)):
coroutine = select
elif isinstance(query, peewee.Update):
coroutine = update
elif isinstance(query, peewee.Insert):
coroutine = insert
elif isinstance(query, peewee.Delete):
coroutine = delete
else:
coroutine = raw_query
return (await coroutine(query))
这样在使用execute()方法时，peewee_async就能识别union。
"""union查询"""
b_query = (Balance.select(
Balance.b.alias('id'), Balance.change,
Balance.total, Balance.addtime
))
i_query = (Integral.select(
Integral.i.alias('id'), Integral.change,
Integral.total, Integral.addtime
))
query_union = await user.object.execute(
(b_query + i_query).order_by(SQL('addtime desc')).limit(2).offset(1)
)
聚合查询
"""聚合函数"""
fn_max = await user.object.scalar(User.select(fn.MAX(User.balance)))
删除操作
await user.object.execute(User.delete().where(User.uid == 10012))
简单的操作先记录到这里，其余操作未完待续~
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