SQLAlchemy 和其他的 ORM 框架

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Python ORM 概览

作为一个美妙的语言，Python 除了 SQLAlchemy 外还有很多ORM库。在这篇文章里，我们将来看看几个流行的可选 ORM 库，以此更好地窥探到Python ORM 境况。通过写一段脚本来读写2个表，person 和 address 到一个简单的数据库，我们能更好地理解每个ORM库的优缺点。

SQLObject

SQLObject 是一个介于SQL数据库和Python之间映射对象的Python ORM。得益于其类似于Ruby on Rails的ActiveRecord模式，在编程社区变得越来越流行。首个 SQLObject在2002年十月发布。它遵循LGPL许可。

在 SQLObject 中，数据库概念是通过与 SLQAlchemy 非常类似的的一种方式映射到Python的，表映射成类，行作为实例而字段作为属性。它同时提供一种基于Python对象的查询语言，这使得 SQL 更加抽象，从而为应用提供了数据库不可知性（译注:应用和数据库分离）。

$ pip install sqlobject

Downloading/unpacking sqlobject

Downloading SQLObject-1.5.1.tar.gz (276kB): 276kB downloaded

Running setup.py egg_info for package sqlobject

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Requirement already satisfied (use --upgrade to upgrade): FormEncode>=1.1.1 in /Users/xiaonuogantan/python2-workspace/lib/python2.7/site-packages (from sqlobject)

Installing collected packages: sqlobject

Running setup.py install for sqlobject

changing mode of build/scripts-2.7/sqlobject-admin from 644 to 755

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changing mode of /Users/xiaonuogantan/python2-workspace/bin/sqlobject-admin to 755

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Successfully installed sqlobject

Cleaning up...

>>> from sqlobject import StringCol, SQLObject, ForeignKey, sqlhub, connectionForURI

>>> sqlhub.processConnection = connectionForURI('sqlite:/:memory:')

>>>

>>> class Person(SQLObject):

... name = StringCol()

...

>>> class Address(SQLObject):

... address = StringCol()

... person = ForeignKey('Person')

...

>>> Person.createTable()

[]

>>> Address.createTable()

上面的代码创建了2个简单的表：person 和 address 。为了创建和插入记录到这2个表，我们简单实例化一个person 实例和一个 address 实例：

>>> p = Person(name='person')

>>> a = Address(address='address', person=p)

>>> p

>>> a

为了获得或检索新记录，我们用神奇的 q 对象关联到 Person 和 Address 类：