import imageio
import os
def export_gif(folder_name, gif_name, fps, name_prefix=''):
    frame_names = [os.path.join(folder_name, f) for f in os.listdir(folder_name)
        if os.path.isfile(os.path.join(folder_name, f)) and f.startswith(name_prefix) and f.endswith('.png')]
    frame_names = sorted(frame_names)

    # Read images.
    images = [imageio.imread(f) for f in frame_names]
    if fps > 0:
        imageio.mimsave(gif_name, images, fps=fps)
    else:
        imageio.mimsave(gif_name, images)