pyqt/basic/layout_1.py

import sys

from PyQt5.QtWidgets import QMainWindow, QApplication, QWidget, QVBoxLayout

from layout_colorwidget import Color


class MainWindow(QMainWindow):

    def __init__(self):
        super().__init__()

        self.setWindowTitle("My App")

        layout = QVBoxLayout()
        layout.addWidget(Color("red"))
        layout.addWidget(Color("green"))
        layout.addWidget(Color("blue"))

        widget = QWidget()
        widget.setLayout(layout)
        self.setCentralWidget(widget)


if __name__ == "__main__":
    app = QApplication(sys.argv)
    window = MainWindow()
    window.show()
    sys.exit(app.exec_())