pyqt widget class for displaying an image. the image resizes to fill the space when the user resizes the desktop window

app.py

## Widget for the single image that is currently on display
class DisplayImage(QWidget):
    def __init__(self, parent=None):
        QWidget.__init__(self)
        self.parent = parent
        self.pixmap = QPixmap()
        self.label = QLabel(self)
        self.assigned_img_full_path = ''

    def update_display_image(self, path_to_image=''):
        self.assigned_img_full_path = path_to_image

        ## render the display image when a thumbnail is selected
        self.on_main_window_resize()

    def on_main_window_resize(self, event=None):
        main_window_size = self.parent.size()
        main_window_height = main_window_size.height()
        main_window_width = main_window_size.width()

        display_image_max_height = main_window_height - 50
        display_image_max_width = main_window_width - 200

        self.pixmap = QPixmap(self.assigned_img_full_path)
        self.pixmap = self.pixmap.scaled(\
            QSize(display_image_max_width, display_image_max_height), \
            Qt.KeepAspectRatio, \
            Qt.SmoothTransformation)

        self.label.setPixmap(self.pixmap)