pyqt widget class for making a thumbnail selector. a user can select thumbnail images that are imported from a photo album folder.

app.py

## Widget for selecting an image in the directory to display
## Makes a vertical scrollable widget with selectable image thumbnails
class ImageFileSelector(QWidget):
    def __init__(self, parent=None, album_path='', display_image=None):
        QWidget.__init__(self, parent=parent)
        self.display_image = display_image
        self.grid_layout = QGridLayout(self)
        self.grid_layout.setVerticalSpacing(30)

        ## Get all the image files in the directory
        files = [f for f in listdir(album_path) if isfile(join(album_path, f))]
        row_in_grid_layout = 0
        first_img_file_path = ''

        ## Render a thumbnail in the widget for every image in the directory
        for file_name in files:
            if filename_has_image_extension(file_name) is False: continue
            img_label = QLabel()
            text_label = QLabel()
            img_label.setAlignment(Qt.AlignCenter)
            text_label.setAlignment(Qt.AlignCenter)
            file_path = album_path + file_name
            pixmap = QPixmap(file_path)
            pixmap = pixmap.scaled(\
                QSize(100, 100), \
                Qt.KeepAspectRatio, \
                Qt.SmoothTransformation)
            img_label.setPixmap(pixmap)
            text_label.setText(file_name)
            img_label.mousePressEvent = \
                lambda e, \
                index=row_in_grid_layout, \
                file_path=file_path: \
                    self.on_thumbnail_click(e, index, file_path)
            text_label.mousePressEvent = img_label.mousePressEvent
            thumbnail = QBoxLayout(QBoxLayout.TopToBottom)
            thumbnail.addWidget(img_label)
            thumbnail.addWidget(text_label)
            self.grid_layout.addLayout( \
                thumbnail, row_in_grid_layout, 0, Qt.AlignCenter)

            if row_in_grid_layout == 0: first_img_file_path = file_path
            row_in_grid_layout += 1

        ## Automatically select the first file in the list during init
        self.on_thumbnail_click(None, 0, first_img_file_path)

    def on_thumbnail_click(self, event, index, img_file_path):
        ## Deselect all thumbnails in the image selector
        for text_label_index in range(len(self.grid_layout)):
            text_label = self.grid_layout.itemAtPosition(text_label_index, 0)\
                .itemAt(1).widget()
            text_label.setStyleSheet("background-color:none;")

        ## Select the single clicked thumbnail
        text_label_of_thumbnail = self.grid_layout.itemAtPosition(index, 0)\
            .itemAt(1).widget()
        text_label_of_thumbnail.setStyleSheet("background-color:blue;")

        ## Update the display's image
        self.display_image.update_display_image(img_file_path)