column_view_extra_column.py

from PySide2 import QtWidgets, QtGui, QtCore


class ColumnView(QtWidgets.QColumnView):
    def __init__(self, parent=None):
        super().__init__(parent)       
        self.model = QtGui.QStandardItemModel()
        self.setModel(self.model)
        self.__get_data()
        self.setColumnWidths([30, 30, 100])
        preview_w = QtWidgets.QPushButton("What's with the extra column? >>>")
        self.setPreviewWidget(preview_w)
        
    def __get_data(self):
        for i in ["a", "b", "c"]:
            item = QtGui.QStandardItem(str(i))
            self.model.appendRow(item)
            for ii in ["d", "e", "f"]:
                item2 = QtGui.QStandardItem(str(ii))
                item.appendRow(item2)
                for iii in ["g", "h", "i"]:
                    item3 = QtGui.QStandardItem(str(iii))
                    item2.appendRow(item3)

if __name__ == '__main__':
    import sys
    args = sys.argv
    app = QtWidgets.QApplication(args)
    w = ColumnView()
    w.show()
    w.resize(800, 500)
    sys.exit(app.exec_())