SQLA QuasiODict

QuasiODict.py

class ProxyODict(object):
    def __init__(self, parent, collection_name, childclass, ordername, keyname, valuename):
        self.parent = parent
        self.collection_name = collection_name
        self.childclass = childclass
        self.ordername = ordername
        self.keyname = keyname
        self.valuename = valuename

    @property
    def collection(self):
        return getattr(self.parent, self.collection_name)

    def keys(self):
        # SQLAQ I feel like SQLA should be able to guarantee
        # that these come back in the right order.  I'm likely
        # using python to sort something SQL could already have sorted for me.
        descriptor = getattr(self.childclass, self.keyname)
        orderer = getattr(self.childclass, self.ordername)
        tmp = list(self.collection.values((orderer,descriptor)))
        tmp.sort()
        return [x[1] for x in tmp]

    def __call__(self,valuename=None):
        keys = self.keys()
        val = valuename or self.valuename
        values = [getattr(self[k],val) for k in keys]
        d = dict(zip(keys,values))
        return d
        
    def __getitem__(self, obj):
        if isinstance(obj,int):
            x = self.collection.filter_by(**{self.ordername:obj}).first()
        elif isinstance(obj,(list,tuple)) and len(obj) == 2:
            x = self.collection.filter_by(**{self.ordername:obj[0],
                                             self.keyname:obj[1]}).first()
        elif isinstance(obj,str):
            raise TypeError("ProxyODict key must be integer or list-like, found {}".format(type(obj)))

        if x:
            return x
        else:
            raise KeyError(obj)

    def __setitem__(self, obj, value):
        try:
            existing = self[obj]
            self.collection.remove(existing)
        except KeyError:
            pass
        # at this point here, you need to pass the length of the collection and the value.  
        # But, but, what about changing the order?  What about duplicated keys? ...TODO
        self.collection.append(value)