Align every widget of a QHBoxLayout to the top

Question

I'm trying to align every widgets in a QHBoxlayout to the top but what I get is every widget seems centered. I think this is due to there different sizes.

For instance with:

from PyQt5.QtGui import *
from PyQt5.QtCore import *
from PyQt5.QtWidgets import *
import sys



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

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

        self.groups = QHBoxLayout()

        l_a1 = QLabel('A')
        a = QVBoxLayout()
        a.addWidget(l_a1)
        self.groups.addLayout(a)

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


        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)
        self.groups.addLayout(a_b_c)

        self.groups.setAlignment(Qt.AlignTop)


        self.wid.setLayout(self.groups)


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

I get :

what I would like instead is something like :

Answer 1

You must apply the alignment to each layout:

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_( ))