blog_example.py

import sys
from PySide2.QtWidgets import QWidget, QPushButton, QVBoxLayout, QHBoxLayout, QApplication


class MainWidget(QWidget):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

        btn1 = QPushButton("button1")
        child = ChildWidget(self)
        main_layout = QVBoxLayout()

        main_layout.addWidget(btn1)
        main_layout.addWidget(child)

        self.setLayout(main_layout)


class ChildWidget(QWidget):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

        btn2 = QPushButton("button2")
        grandson = GrandsonWidget(self)
        child_layout = QHBoxLayout()

        child_layout.addWidget(btn2)
        child_layout.addWidget(grandson)

        self.setLayout(child_layout)


class GrandsonWidget(QWidget):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

        btn3 = QPushButton("button3")
        btn4 = QPushButton("button4")
        grandson_layout = QVBoxLayout()

        grandson_layout.addWidget(btn3)
        grandson_layout.addWidget(btn4)

        self.setLayout(grandson_layout)


if __name__ == '__main__':
    app = QApplication(sys.argv)
    wdt = MainWidget()
    wdt.show()
    sys.exit(app.exec_())