QDataFrame

class QSeries(pd.Series):
    _metadata = ["unit", "descriptor"]
    @property
    def _constructor(self):
        return QSeries

    @property
    def _constructor_expanddim(self):
        return QDataFrame


class QDataFrame(pd.DataFrame):
    # normal properties
    _metadata = ["units"]
    def __init__(self, *args, units=None, **kwargs):
        super(QDataFrame, self).__init__(*args, **kwargs)
        if units is None:
            self.units = {}
        else:
            self.units = {key:value for key, value in units.items() if key in self.columns}
        for col in self.columns:
            if col in self.units:
                self[col].unit = self.units[col]
    @property
    def _constructor(self):
        return QDataFrame
        
    @property
    def _constructor_sliced(self):
        return QSeries