十二、python基础(Twsited异步网络框架、SqlAlchemy ORM)

Twsited异步网络框架

Twisted是一个事件驱动的网络框架，其中包含了诸多功能，例如：网络协议、线程、数据库管理、网络操作、电子邮件等。　

事件驱动

简而言之，事件驱动分为二个部分：第一，注册事件；第二，触发事件。

自定义事件驱动框架：

#!/usr/bin/env python
# -*- coding:utf-8 -*-
 
# event_drive.py
 
event_list = []
 
 
def run():
    for event in event_list:
        obj = event()
        obj.execute()
 
 
class BaseHandler(object):
    """
    用户必须继承该类，从而规范所有类的方法（类似于接口的功能）
    """
    def execute(self):
        raise Exception('you must overwrite execute')
 
最牛逼的事件驱动框架

程序员使用框架”：　　

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#!/usr/bin/env python
# -*- coding:utf-8 -*-
 
from source import event_drive
 
 
class MyHandler(event_drive.BaseHandler):
 
    def execute(self):
        print 'event-drive execute MyHandler'
 
 
event_drive.event_list.append(MyHandler)
event_drive.run()

 

Protocols

Protocols描述了如何以异步的方式处理网络中的事件。HTTP、DNS以及IMAP是应用层协议中的例子。Protocols实现了IProtocol接口，它包含如下的方法：

makeConnection               在transport对象和服务器之间建立一条连接
connectionMade               连接建立起来后调用
dataReceived                 接收数据时调用
connectionLost               关闭连接时调用

Transports

Transports代表网络中两个通信结点之间的连接。Transports负责描述连接的细节，比如连接是面向流式的还是面向数据报的，流控以及可靠性。TCP、UDP和Unix套接字可作为transports的例子。它们被设计为“满足最小功能单元，同时具有最大程度的可复用性”，而且从协议实现中分离出来，这让许多协议可以采用相同类型的传输。Transports实现了ITransports接口，它包含如下的方法：

write                   以非阻塞的方式按顺序依次将数据写到物理连接上
writeSequence           将一个字符串列表写到物理连接上
loseConnection          将所有挂起的数据写入，然后关闭连接
getPeer                 取得连接中对端的地址信息
getHost                 取得连接中本端的地址信息

将transports从协议中分离出来也使得对这两个层次的测试变得更加简单。可以通过简单地写入一个字符串来模拟传输，用这种方式来检查。

EchoServer

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from twisted.internet import protocol
from twisted.internet import reactor
 
class Echo(protocol.Protocol):
    def dataReceived(self, data):
        self.transport.write(data)
 
def main():
    factory = protocol.ServerFactory()
    factory.protocol = Echo
 
    reactor.listenTCP(1234,factory)
    reactor.run()
 
if __name__ == '__main__':
    main()

　　

EchoClient

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from twisted.internet import reactor, protocol
 
 
# a client protocol
 
class EchoClient(protocol.Protocol):
    """Once connected, send a message, then print the result."""
 
    def connectionMade(self):
        self.transport.write("hello alex!")
 
    def dataReceived(self, data):
        "As soon as any data is received, write it back."
        print "Server said:", data
        self.transport.loseConnection()
 
    def connectionLost(self, reason):
        print "connection lost"
 
class EchoFactory(protocol.ClientFactory):
    protocol = EchoClient
 
    def clientConnectionFailed(self, connector, reason):
        print "Connection failed - goodbye!"
        reactor.stop()
 
    def clientConnectionLost(self, connector, reason):
        print "Connection lost - goodbye!"
        reactor.stop()
 
 
# this connects the protocol to a server running on port 8000
def main():
    f = EchoFactory()
    reactor.connectTCP("localhost", 1234, f)
    reactor.run()
 
# this only runs if the module was *not* imported
if __name__ == '__main__':
    main()

运行服务器端脚本将启动一个TCP服务器，监听端口1234上的连接。服务器采用的是Echo协议，数据经TCP transport对象写出。运行客户端脚本将对服务器发起一个TCP连接，回显服务器端的回应然后终止连接并停止reactor事件循环。这里的Factory用来对连接的双方生成protocol对象实例。两端的通信是异步的，connectTCP负责注册回调函数到reactor事件循环中，当socket上有数据可读时通知回调处理

一个传送文件的例子 

server side 

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#_*_coding:utf-8_*_
# This is the Twisted Fast Poetry Server, version 1.0
 
import optparse, os
 
from twisted.internet.protocol import ServerFactory, Protocol
 
 
def parse_args():
    usage = """usage: %prog [options] poetry-file
 
This is the Fast Poetry Server, Twisted edition.
Run it like this:
 
  python fastpoetry.py <path-to-poetry-file>
 
If you are in the base directory of the twisted-intro package,
you could run it like this:
 
  python twisted-server-1/fastpoetry.py poetry/ecstasy.txt
 
to serve up John Donne's Ecstasy, which I know you want to do.
"""
 
    parser = optparse.OptionParser(usage)
 
    help = "The port to listen on. Default to a random available port."
    parser.add_option('--port', type='int', help=help)
 
    help = "The interface to listen on. Default is localhost."
    parser.add_option('--iface', help=help, default='localhost')
 
    options, args = parser.parse_args()
    print("--arg:",options,args)
 
    if len(args) != 1:
        parser.error('Provide exactly one poetry file.')
 
    poetry_file = args[0]
 
    if not os.path.exists(args[0]):
        parser.error('No such file: %s' % poetry_file)
 
    return options, poetry_file
 
 
class PoetryProtocol(Protocol):
 
    def connectionMade(self):
        self.transport.write(self.factory.poem)
        self.transport.loseConnection()
 
 
class PoetryFactory(ServerFactory):
 
    protocol = PoetryProtocol
 
    def __init__(self, poem):
        self.poem = poem
 
 
def main():
    options, poetry_file = parse_args()
 
    poem = open(poetry_file).read()
 
    factory = PoetryFactory(poem)
 
    from twisted.internet import reactor
 
    port = reactor.listenTCP(options.port or 9000, factory,
                             interface=options.iface)
 
    print 'Serving %s on %s.' % (poetry_file, port.getHost())
 
    reactor.run()
 
 
if __name__ == '__main__':
    main()

client side 　　

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# This is the Twisted Get Poetry Now! client, version 3.0.
 
# NOTE: This should not be used as the basis for production code.
 
import optparse
 
from twisted.internet.protocol import Protocol, ClientFactory
 
 
def parse_args():
    usage = """usage: %prog [options] [hostname]:port ...
 
This is the Get Poetry Now! client, Twisted version 3.0
Run it like this:
 
  python get-poetry-1.py port1 port2 port3 ...
"""
 
    parser = optparse.OptionParser(usage)
 
    _, addresses = parser.parse_args()
 
    if not addresses:
        print parser.format_help()
        parser.exit()
 
    def parse_address(addr):
        if ':' not in addr:
            host = '127.0.0.1'
            port = addr
        else:
            host, port = addr.split(':', 1)
 
        if not port.isdigit():
            parser.error('Ports must be integers.')
 
        return host, int(port)
 
    return map(parse_address, addresses)
 
 
class PoetryProtocol(Protocol):
 
    poem = ''
 
    def dataReceived(self, data):
        self.poem += data
 
    def connectionLost(self, reason):
        self.poemReceived(self.poem)
 
    def poemReceived(self, poem):
        self.factory.poem_finished(poem)
 
 
class PoetryClientFactory(ClientFactory):
 
    protocol = PoetryProtocol
 
    def __init__(self, callback):
        self.callback = callback
 
    def poem_finished(self, poem):
        self.callback(poem)
 
 
def get_poetry(host, port, callback):
    """
    Download a poem from the given host and port and invoke
 
      callback(poem)
 
    when the poem is complete.
    """
    from twisted.internet import reactor
    factory = PoetryClientFactory(callback)
    reactor.connectTCP(host, port, factory)
 
 
def poetry_main():
    addresses = parse_args()
 
    from twisted.internet import reactor
 
    poems = []
 
    def got_poem(poem):
        poems.append(poem)
        if len(poems) == len(addresses):
            reactor.stop()
 
    for address in addresses:
        host, port = address
        get_poetry(host, port, got_poem)
 
    reactor.run()
 
    for poem in poems:
        print poem
 
 
if __name__ == '__main__':
    poetry_main()

Twisted深入

http://krondo.com/an-introduction-to-asynchronous-programming-and-twisted/ 

http://blog.csdn.net/hanhuili/article/details/9389433 

 

SqlAlchemy ORM　　

SQLAlchemy是Python编程语言下的一款ORM框架，该框架建立在数据库API之上，使用关系对象映射进行数据库操作，简言之便是：将对象转换成SQL，然后使用数据API执行SQL并获取执行结果

 

Dialect用于和数据API进行交流，根据配置文件的不同调用不同的数据库API，从而实现对数据库的操作，如：

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MySQL-Python
    mysql+mysqldb://<user>:<password>@<host>[:<port>]/<dbname>
  
pymysql
    mysql+pymysql://<username>:<password>@<host>/<dbname>[?<options>]
  
MySQL-Connector
    mysql+mysqlconnector://<user>:<password>@<host>[:<port>]/<dbname>
  
cx_Oracle
    oracle+cx_oracle://user:pass@host:port/dbname[?key=value&key=value...]
  
更多详见：http://docs.sqlalchemy.org/en/latest/dialects/index.html
　

步骤一：

使用 Engine/ConnectionPooling/Dialect 进行数据库操作，Engine使用ConnectionPooling连接数据库，然后再通过Dialect执行SQL语句。

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#!/usr/bin/env python
# -*- coding:utf-8 -*-
  
from sqlalchemy import create_engine
  
  
engine = create_engine("mysql+mysqldb://root:123@127.0.0.1:3306/s11", max_overflow=5)
  
engine.execute(
    "INSERT INTO ts_test (a, b) VALUES ('2', 'v1')"
)
  
engine.execute(
     "INSERT INTO ts_test (a, b) VALUES (%s, %s)",
    ((555, "v1"),(666, "v1"),)
)
engine.execute(
    "INSERT INTO ts_test (a, b) VALUES (%(id)s, %(name)s)",
    id=999, name="v1"
)
  
result = engine.execute('select * from ts_test')
result.fetchall()

　　

步骤二：

使用 Schema Type/SQL Expression Language/Engine/ConnectionPooling/Dialect 进行数据库操作。Engine使用Schema Type创建一个特定的结构对象，之后通过SQL Expression Language将该对象转换成SQL语句，然后通过 ConnectionPooling 连接数据库，再然后通过 Dialect 执行SQL，并获取结果。

#!/usr/bin/env python
# -*- coding:utf-8 -*-
 
from sqlalchemy import create_engine, Table, Column, Integer, String, MetaData, ForeignKey
 
metadata = MetaData()
 
user = Table('user', metadata,
    Column('id', Integer, primary_key=True),
    Column('name', String(20)),
)
 
color = Table('color', metadata,
    Column('id', Integer, primary_key=True),
    Column('name', String(20)),
)
engine = create_engine("mysql+mysqldb://root@localhost:3306/test", max_overflow=5)
 
metadata.create_all(engine)

增删改查

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#!/usr/bin/env python
# -*- coding:utf-8 -*-
 
from sqlalchemy import create_engine, Table, Column, Integer, String, MetaData, ForeignKey
 
metadata = MetaData()
 
user = Table('user', metadata,
    Column('id', Integer, primary_key=True),
    Column('name', String(20)),
)
 
color = Table('color', metadata,
    Column('id', Integer, primary_key=True),
    Column('name', String(20)),
)
engine = create_engine("mysql+mysqldb://root:123@127.0.0.1:3306/s11", max_overflow=5)
 
conn = engine.connect()
 
# 创建SQL语句，INSERT INTO "user" (id, name) VALUES (:id, :name)
conn.execute(user.insert(),{'id':7,'name':'seven'})
conn.close()
 
# sql = user.insert().values(id=123, name='wu')
# conn.execute(sql)
# conn.close()
 
# sql = user.delete().where(user.c.id > 1)
 
# sql = user.update().values(fullname=user.c.name)
# sql = user.update().where(user.c.name == 'jack').values(name='ed')
 
# sql = select([user, ])
# sql = select([user.c.id, ])
# sql = select([user.c.name, color.c.name]).where(user.c.id==color.c.id)
# sql = select([user.c.name]).order_by(user.c.name)
# sql = select([user]).group_by(user.c.name)
 
# result = conn.execute(sql)
# print result.fetchall()
# conn.close()

 

一个简单的完整例子

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from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String
from  sqlalchemy.orm import sessionmaker
 
Base = declarative_base() #生成一个SqlORM 基类
 
 
engine = create_engine("mysql+mysqldb://root@localhost:3306/test",echo=False)
 
 
class Host(Base):
    __tablename__ = 'hosts'
    id = Column(Integer,primary_key=True,autoincrement=True)
    hostname = Column(String(64),unique=True,nullable=False)
    ip_addr = Column(String(128),unique=True,nullable=False)
    port = Column(Integer,default=22)
 
Base.metadata.create_all(engine) #创建所有表结构
 
if __name__ == '__main__':
    SessionCls = sessionmaker(bind=engine) #创建与数据库的会话session class ,注意,这里返回给session的是个class,不是实例
    session = SessionCls()
    #h1 = Host(hostname='localhost',ip_addr='127.0.0.1')
    #h2 = Host(hostname='ubuntu',ip_addr='192.168.2.243',port=20000)
    #h3 = Host(hostname='ubuntu2',ip_addr='192.168.2.244',port=20000)
    #session.add(h3)
    #session.add_all( [h1,h2])
    #h2.hostname = 'ubuntu_test' #只要没提交,此时修改也没问题
    #session.rollback()
    #session.commit() #提交
    res = session.query(Host).filter(Host.hostname.in_(['ubuntu2','localhost'])).all()
    print(res)

　　

更多内容详见：

    http://www.jianshu.com/p/e6bba189fcbd

    http://docs.sqlalchemy.org/en/latest/core/expression_api.html

注：SQLAlchemy无法修改表结构，如果需要可以使用SQLAlchemy开发者开源的另外一个软件Alembic来完成。

步骤三：

使用 ORM/Schema Type/SQL Expression Language/Engine/ConnectionPooling/Dialect 所有组件对数据进行操作。根据类创建对象，对象转换成SQL，执行SQL。

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#!/usr/bin/env python
# -*- coding:utf-8 -*-
  
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String
from sqlalchemy.orm import sessionmaker
from sqlalchemy import create_engine
  
engine = create_engine("mysql+mysqldb://root:123@127.0.0.1:3306/s11", max_overflow=5)
  
Base = declarative_base()
  
  
class User(Base):
    __tablename__ = 'users'
    id = Column(Integer, primary_key=True)
    name = Column(String(50))
  
# 寻找Base的所有子类，按照子类的结构在数据库中生成对应的数据表信息
# Base.metadata.create_all(engine)
  
Session = sessionmaker(bind=engine)
session = Session()
  
  
# ########## 增 ##########
# u = User(id=2, name='sb')
# session.add(u)
# session.add_all([
#     User(id=3, name='sb'),
#     User(id=4, name='sb')
# ])
# session.commit()
  
# ########## 删除 ##########
# session.query(User).filter(User.id > 2).delete()
# session.commit()
  
# ########## 修改 ##########
# session.query(User).filter(User.id > 2).update({'cluster_id' : 0})
# session.commit()
# ########## 查 ##########
# ret = session.query(User).filter_by(name='sb').first()
  
# ret = session.query(User).filter_by(name='sb').all()
# print ret
  
# ret = session.query(User).filter(User.name.in_(['sb','bb'])).all()
# print ret
  
# ret = session.query(User.name.label('name_label')).all()
# print ret,type(ret)
  
# ret = session.query(User).order_by(User.id).all()
# print ret
  
# ret = session.query(User).order_by(User.id)[1:3]
# print ret
# session.commit()

外键关联

A one to many relationship places a foreign key on the child table referencing the parent.relationship() is then specified on the parent, as referencing a collection of items represented by the child

from sqlalchemy import Table, Column, Integer, ForeignKey
from sqlalchemy.orm import relationship
from sqlalchemy.ext.declarative import declarative_base

Base = declarative_base()
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<br>class Parent(Base):
    __tablename__ = 'parent'
    id = Column(Integer, primary_key=True)
    children = relationship("Child")
 
class Child(Base):
    __tablename__ = 'child'
    id = Column(Integer, primary_key=True)
    parent_id = Column(Integer, ForeignKey('parent.id'))

To establish a bidirectional relationship in one-to-many, where the “reverse” side is a many to one, specify an additional relationship() and connect the two using therelationship.back_populates parameter:

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class Parent(Base):
    __tablename__ = 'parent'
    id = Column(Integer, primary_key=True)
    children = relationship("Child", back_populates="parent")
 
class Child(Base):
    __tablename__ = 'child'
    id = Column(Integer, primary_key=True)
    parent_id = Column(Integer, ForeignKey('parent.id'))
    parent = relationship("Parent", back_populates="children")

Child will get a parent attribute with many-to-one semantics.

Alternatively, the backref option may be used on a single relationship() instead of usingback_populates:

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class Parent(Base):
    __tablename__ = 'parent'
    id = Column(Integer, primary_key=True)
    children = relationship("Child", backref="parent")

　　　　

附，原生sql join查询

几个Join的区别 http://stackoverflow.com/questions/38549/difference-between-inner-and-outer-joins 

  • INNER JOIN: Returns all rows when there is at least one match in BOTH tables
  • LEFT JOIN: Return all rows from the left table, and the matched rows from the right table
  • RIGHT JOIN: Return all rows from the right table, and the matched rows from the left table
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select host.id,hostname,ip_addr,port,host_group.name from host right join host_group on host.id = host_group.host_id

in SQLAchemy

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session.query(Host).join(Host.host_groups).filter(HostGroup.name=='t1').group_by("Host").all()

　　

group by 查询

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select name,count(host.id) as NumberOfHosts from host right join host_group on host.id= host_group.host_id group by name;

in SQLAchemy

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from sqlalchemy import func
session.query(HostGroup, func.count(HostGroup.name )).group_by(HostGroup.name).all()
 
#another example
session.query(func.count(User.name), User.name).group_by(User.name).all() SELECT count(users.name) AS count_1, users.name AS users_name
FROM users GROUP BY users.name

 

posted @ 2018-10-10 07:01  一叶风语  阅读(893)  评论(0)  编辑  收藏  举报