Python pick 20 random results from list

I would like to get 20 random results from the following list

coordinaten = [[20, 140], [40, 140], [60, 140], [80, 140], [100, 140], [120, 140],
           [20, 120], [40, 120], [60, 120], [80, 120], [100, 120], [120, 120],
           [20, 100], [40, 100], [60, 100], [80, 100], [100, 100], [120, 100],
           [20, 80], [40, 80], [60, 80], [80, 80], [100, 80], [120, 80],
           [20, 60], [40, 60], [60, 60], [80, 60], [100, 60], [120, 60],
           [20, 40], [40, 40], [60, 40], [80, 40], [100, 40], [120, 40]]

I tried random.shuffle but it returns me an empty list.

I hope someone can help me out.

EDIT:

Got it working, didn't know you could give an parameter to random.shuffle() Thanks for your replies.