我如何从 psycopg2 继承? [英] How can I inherit from psycopg2?

问题描述

我正在尝试像这样继承 psycopg2:

I'm trying inherit psycopg2 like this:

import psycopg2

class myp(psycopg):
    pass

ii = myp
ii.connect(database = "myDataBase", user = "myUser", password="myPassword")

然后它抛出一个错误:

class myp(psycopg2._psycopg):
TypeError: Error when calling the metaclass bases
module.__init__() takes at most 2 arguments (3 given)

是否可以从 psycopg2 库中继承?

Is it possible to inherit from psycopg2 library?

我想使用不同的数据库，所以我只需要更改 MyDatabase 类.像包装纸一样的东西.例子:

I want to use different databases, so I just have to change the class MyDatabase. something like a wrapper. example:

import psycopg2

class MyDatabase(psycopg2):
    def connect(self):
        #do some stuff
        return psycopg2.connect(database = "myDataBase", user = "myUser",   password="myPassword")

对于 mysqldb导入 MySQL 数据库

for mysqldb import MySQLdb

class MyDatabase(MySQLdb)
    def connect(self):
        #do some stuff
        return psycopg2.connect(database = "myDataBase", user = "myUser", password="myPassword")

和派生类类 MyDataBaseApp(MyDatabase):def add(self, myObjectClass):db = MyDatabase()cn = 无

and derived class class MyDataBaseApp(MyDatabase): def add(self, myObjectClass): db = MyDatabase() cn = None

        try:
            cn = db.connect()
            cur = cn.cursor()
            cur.execute ("INSERT ...",(myObjectClass.parameter1, myObjectClass.parameter2))
            cn.commit()
        except MyDatabase.DatabaseError, e:
            print e
            if cn:
                cn.rollback()
        finally:
            if cn:
                cn.close()

但根据文档我必须以另一种方式做，建议?

but according to the documentation I have to do it another way, suggestions?

推荐答案

Disclaimer: 我不熟悉 psycopg

Disclaimer: I'm not familiar with psycopg

更新

似乎文档建议对psycopg2进行子类化.extensions.connection.然后，connect() 是一个仍可用于创建新连接的工厂函数，但您必须将您的类作为工厂提供，同样 根据文档

Seems the documentation recommends to subclass psycopg2.extensions.connection. Then, connect() is a factory function that can still be used to create new connections, but you have to provide your class as a factory, again according to the docs

完整的代码可能看起来更像(未经测试):

Full code may have to look more like (untested):

import psycopg2

class myp(psycopg2.extensions.connection):
    pass

ii = connect(connection_factory=myp,
             database = "myDataBase", user = "myUser", password="myPassword")

更新 2

使用更新的方法，您正在尝试构建具有不同/不同接口的新类.通常，组合比继承更好，参见 wikipedia 和 这个问题.

With the updated approach, you're trying to build new classes with different/divergent interfaces. Often, composition is better than inheritance, see wikipedia and this question.

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