Set background image and display mode in gsettings: subprocess.run(), click

set_bg_img.py

#! /bin/python3
'''`set_bg_img` module contains `set_img()` method which sets image URI and display mode.
$ python3 set_bg_img.py'''
from subprocess import run
from click import command
from click import option
from click import Choice


@command()  # command options
@option('--img', prompt='Image file')  # image URI option
@option('--mode', type=Choice(['wallpaper', 'centered', 'scaled', 'stretched',
                               'zoom', 'spanned']), prompt='Display mode')  # display mode option
def set_img(img, mode):
    '''Set wallpaper image URI and display mode.'''
    run(['gsettings', 'set', 'org.gnome.desktop.background',
         'picture-options', mode], check=True)  # set display mode
    run(['gsettings', 'set', 'org.gnome.desktop.background',
         'picture-uri', f'file:///home/foo/Pictures/{img}'], check=True)  # set image URI


if __name__ == '__main__':
    set_img()  # if standalone

User prompted for image file URI and display mode:

$ python3 set_bg_img.py 
Image file: foo.jpg
Display mode (wallpaper, centered, scaled, stretched, zoom, spanned): wallpaper