Python:如何成功继承Sqlite3.Cursor并添加我自定义的方法

问题描述

我想创建自己的 MagicCursor 类.我希望它从 sqlite3.Cursor() 继承所有方法和属性.但在他的情况下看起来并不那么容易.

I want to make my own MagicCursor class. I want it to inherit all method and attributes from sqlite3.Cursor(). But it looks not that easy in t his case.

通常我们会像这样创建一个游标:

usually we create a cursor like this:

import sqlite3
conn = sqlite3.connect('test.db')
crs = conn.cursor()

因为两者之间存在联系.所以我想我必须定义我自己的Connection Class，然后定义我自己的Cursor.

because there's a connection in between. So I think I have to define my own Connection Class and then define my own Cursor.

这是我想要实现的:

import sqlite3
conn = MyConnect('test.db') ## this returns me a connect object, inherit from         sqlite3.Connection 
crs = conn.cursor() ## this returns me a MyCursor class,
                ## which inherit from sqlite3.Cursor() and has my customized method

这是我的代码，但失败了.

Here's my code, but failed.

class MyConnect(sqlite3.Connection):
    def cursor(self):
        return MyCursor(self)

class MyCursor(sqlite3.cursor):
    def __init__(self, connect):
        self = connect.cursor()

    def mymethod1(self, argv)
         ...... return ...... ## what ever I defined

有人知道如何实现吗?

推荐答案

import sqlite3
class MyConnect(sqlite3.Connection):
    def cursor(self):
        return super(MyConnect, self).cursor(MyCursor)

class MyCursor(sqlite3.Cursor):
    def mymethod1(self, argv):
        print('Got here')

conn = sqlite3.connect(':memory:', factory=MyConnect)
print(conn)
# <__main__.MyConnect object at 0x90db66c>

cursor = conn.cursor()
print(cursor)
# <__main__.MyCursor object at 0x90d19dc>

cursor.mymethod1('foo')
# Got here

在这个例子中，super(MyConnect, self).cursor(MyCursor) 调用sqlite3.Connection.cursor(MyCursor).

In this example, super(MyConnect, self).cursor(MyCursor) callssqlite3.Connection.cursor(MyCursor).

sqlite3.Connection.cursor 接受一个可选的参数，cursorClass.提供时，即用于实例化游标的类.

sqlite3.Connection.cursor accepts an optional argument, cursorClass. When supplied, that is the class used to instantiate the cursor.

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