Example of using QTreeView with QAbstractItemModel from https://www.hardcoded.net/articles/using_qtreeview_with_qabstractitemmodel

app.py

if __name__ == "__main__":

    from PyQt5.QtCore import QAbstractItemModel, QFile, QIODevice, QModelIndex, Qt
    from PyQt5.QtWidgets import QApplication, QTreeView
    import sys
    from tree_model import TreeModel, TreeNode, RefNode


    class NamedElement(object):  # your internal structure
        def __init__(self, name, subelements):
            super(NamedElement, self).__init__()
            self.name = name
            self.subelements = subelements

        def __repr__(self):
            return "NamedElement(name='{}', subelements={})".format(
                self.name, [x.name for x in self.subelements]
            )

    class NamedNode(TreeNode):
        def __init__(self, ref, parent, row):
            self.ref = ref
            super(NamedNode, self).__init__(ref, parent, row)

        def _getChildren(self):
            return self.ref.subelements

        def _createNode(self, ref, row):
            # print("NamedNode._createNode  ref: '{}', row: '{}'".format(ref, row))
            return NamedNode(ref, self, row)


    class NamesModel(TreeModel):
        def __init__(self, rootElements, **kwargs):
            self.rootElements = rootElements
            super(NamesModel, self).__init__(**kwargs)

        def _getRootNodes(self):
            return [
                NamedNode(elem, None, index)
                for index, elem in enumerate(self.rootElements)
            ]

        def columnCount(self, parent):
            return 1

        def data(self, index, role):
            if not index.isValid():
                return None
            node = index.internalPointer()
            if role == Qt.DisplayRole and index.column() == 0:
                return node.ref.name
            return None

        def headerData(self, section, orientation, role):
            if orientation == Qt.Horizontal and role == Qt.DisplayRole and section == 0:
                return "Name"
            return None

        def _getChildren(self):
            # Returns the actual domain objects
            return [n.ref for n in self._getRootNodes()]

        def _createNode(self, ref, row):
            print("NamesModel._createNode  ref: '{}', row: '{}'".format(ref, row))
            return NamedNode(ref, None, row)
            raise ValueError("NamesModel _createNode")
            

    app = QApplication(sys.argv)

    elements = [
        NamedElement("A", [NamedElement("B", [NamedElement("C", [])])]),
        NamedElement("D", []),
        NamedElement("E", []),
    ]
    model = NamesModel(elements)
    view = QTreeView()
    view.setModel(model)
    view.setWindowTitle("Simple Tree Model")
    view.show()
    sys.exit(app.exec_())