How to redirect to another page when drop button is selected with flask?

    
        Select label type 
        {% for image_name in image_names %}
        {{image_name}}
        {%endfor%} 
    

@app.route('/gallery_new', methods=["GET", "POST"])
def get_gallery_new():

    folder_path = request.form.get('cadlists')

    all_imgs = os.listdir(folder_path)
    all_imgs_val = 0
    img_paths = os.listdir(os.path.join(folder_path,all_imgs[all_imgs_val]))
    cls_name = all_imgs[all_imgs_val]
    return render_template('gallery.html',image_names = all_imgs,img_paths=img_paths,folder_path=folder_path,cls_name=cls_name)