PyQT5 - align left

[frohr]

buttonbox3 = QHBoxLayout()

class MainWindow(QtWidgets.QMainWindow):

    def __init__(self, *args, **kwargs):
        super(MainWindow, self).__init__(*args, **kwargs)
        self.canvas = MplCanvas(self, width=5, height=4, dpi=100)
        self.setCentralWidget(self.canvas)
        self.showMaximized() 
        toolbar = NavigationToolbar(self.canvas, self)
        layout = QtWidgets.QVBoxLayout()
      
        buttonbox = QHBoxLayout()  
        buttonbox2 = QHBoxLayout() 
        buttonbox3 = QHBoxLayout()