pyqt5 : widget alignment in layout

align_widget.py

class SurfViewer(QMainWindow):
    def __init__(self, parent=None):
        super(SurfViewer, self).__init__(parent=parent)
        self.setFixedSize(300, 100)

        self.wid = QWidget()
        self.setCentralWidget(self.wid)

        self.groups = QHBoxLayout(self.wid)

        l_a1 = QLabel('A')
        a = QVBoxLayout()
        a.addWidget(l_a1)

        l_a2 = QLabel('A')
        l_b2 = QLabel('B')
        a_b = QVBoxLayout()
        a_b.addWidget(l_a2)
        a_b.addWidget(l_b2)

        l_a3 = QLabel('A')
        l_b3 = QLabel('B')
        l_c3 = QLabel('C')
        a_b_c = QVBoxLayout()
        a_b_c.addWidget(l_a3)
        a_b_c.addWidget(l_b3)
        a_b_c.addWidget(l_c3)

        a.setAlignment(Qt.AlignTop)
        a_b.setAlignment(Qt.AlignTop)
        a_b_c.setAlignment(Qt.AlignTop)

        self.groups.addLayout(a)
        self.groups.addLayout(a_b)
        self.groups.addLayout(a_b_c)
        self.groups.setAlignment(Qt.AlignTop)


if __name__ == '__main__':
    app = QApplication(sys.argv)
    ex = SurfViewer()
    ex.setWindowTitle('window')
    ex.show()
    sys.exit(app.exec_( ))

https://stackoverflow.com/questions/49127653/align-every-widget-of-a-qhboxlayout-to-the-top