alignButton.py

class MyButton(QtWidgets.QPushButton):
    def __init__(self, *args, **kwargs):
        super(MyButton, self).__init__(*args, **kwargs)

    def setPixmap(self, pixmap):
        self.pixmap = pixmap

    def sizeHint(self):
        parent_size = QtWidgets.QPushButton.sizeHint(self)
        return QtCore.QSize(parent_size.width() + self.pixmap.width(), max(parent_size.height(), self.pixmap.height()))

    def paintEvent(self, event):
        QtWidgets.QPushButton.paintEvent(self, event)

        pos_x = 5  # hardcoded horizontal margin
        pos_y = (self.height() - self.pixmap.height()) / 2

        painter = QtGui.QPainter(self)
        painter.setRenderHint(QtGui.QPainter.Antialiasing, True)
        painter.setRenderHint(QtGui.QPainter.SmoothPixmapTransform, True)
        painter.drawPixmap(pos_x, pos_y, self.pixmap)


class TestUI(QtWidgets.QWidget):
    def __init__(self, parent=None):
        super(TestUI, self).__init__(parent)

        # initialization object
        layout = QtWidgets.QGridLayout()
        pb = MyButton('test')
        
        path = r"xxx"
        pixmap = QtGui.QPixmap(path).scaled(40, 40, QtCore.Qt.KeepAspectRatio, QtCore.Qt.SmoothTransformation)
        pb.setPixmap(pixmap)

        layout.addWidget(pb)
        self.setLayout(layout)  

in case you don't assign an icon, but use this class for all buttons, I've added a try-excpet block:

def sizeHint(self):
       parent_size = QPushButton.sizeHint(self)
       try:
           return QSize(
               parent_size.width() + self.pixmap.width(),
               max(parent_size.height(),
                   self.pixmap.height()))
       except AttributeError as error:
           return QSize(
               parent_size.width(),
               parent_size.height())
           logging.debug(error)

and

def paintEvent(self, event):
        QPushButton.paintEvent(self, event)

        try:
            pos_x = 5  # hardcoded horizontal margin
            pos_y = (self.height() - self.pixmap.height()) / 2

            painter = QPainter(self)
            painter.setRenderHint(QPainter.Antialiasing, True)
            painter.setRenderHint(QPainter.SmoothPixmapTransform, True)
            painter.drawPixmap(pos_x, pos_y, self.pixmap)
        except AttributeError as error:
            logging.debug(error)

thanx for your work