问题
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)
Here is how I initialize the table:
testTable = Table('BestTable', test = 'TestType', test2='INT')
It works as expected the only thing if I try:
testTable[0]['test'] = "LALALA"
It does nothing, on the other hand this updates rather than overwrites the table:
testTable[0] = {"test": "LALALA"}
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!
回答1:
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
then return that instead of a regular dict
:
def getBufferRow(self, index):
row = {}
for key in self.columns:
row[key] = self.columns[key][index]
return Row(self, index, row)
来源:https://stackoverflow.com/questions/15417962/getitem-setitem-multiple-keys-python