__getitem__，__setitem__多重键Python [英] __getitem__, __setitem__ multiple keys Python

问题描述

我试图创建一个类，将数据存储在本地缓冲区以及充当数据库的接口。我有以下代码：

I am trying to create a class that stores data in a local buffer as well as acts as an interface to a database. I've got following code:

class Table(object):    
    def __init__(self, tableName, **columnDict):
       self.tableName      = tableName
       self.columns        = {}
       self.types          = {}
       self.columns['id']  = []
       self.types['id']    = 'INT PRIMARY KEY NOT NULL'
       for name in columnDict:
           self.columns[name] = []
           self.types[name]    = columnDict[name]

    def updateBufferRow(self, index, updateDict):
       for key in updateDict:
           self.columns[key][index] = updateDict[key]

    def getBufferRow(self, index):
       row = {}
       for key in self.columns:
           row[key] = self.columns[key][index]
       return row

    def __getitem__(self, key, **args):
       """ Allows using self[key] method """
       return self.getBufferRow(key)

    def __setitem__(self, key, value, **args):
       """ Allows using self[key] = value method """
       self.updateBufferRow(key, value)

这是我如何初始化表：

testTable = Table('BestTable', test = 'TestType', test2='INT')

只要我尝试就可以了：

testTable[0]['test'] = "LALALA"

另一方面，此更新而不是覆盖表：

It does nothing, on the other hand this updates rather than overwrites the table:

testTable[0] = {"test": "LALALA"}

我知道我必须重写updateBufferRow（）和getBufferRow（）方法，相当肯定是如何使用__getitem__和__setitem__方法获取多个键
任何帮助/提示将非常感谢。

I know I have to rewrite updateBufferRow() and getBufferRow() methods, the only thing I am not quite sure is how to get multiple keys using __getitem__ and __setitem__ methods Any help/hints will be greatly appreciated. Thank you guys!

推荐答案

您的<$ c>返回的 dict $ c> __ getitem __ 与您的列没有任何关系。你需要返回一个看起来像 dict 但是映射 __ setattr __ 的回调到你的表列： / p>

The dict returned by your __getitem__ has no relation any more with your columns. You'll need to return something that perhaps looks like a dict but maps __setattr__ calls back to your table columns:

class Row(dict):
    def __init__(self, table, index, *args, **kw):
        self._table, self._index = table, index
        super(Row, self).__init__(*args, **kw)

    def __setitem__(self, key, value):
        super(Row, self).__setitem__(key, value)
        self._table.columns[key][self._index] = value

然后返回而不是常规 dict ：

def getBufferRow(self, index):
   row = {}
   for key in self.columns:
       row[key] = self.columns[key][index]
   return Row(self, index, row)

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