ratings = {'Shane': {'127 Hours': 5.0, 'Avatar': 4.0, 'Nonstop': 5.0},
    'Joe': {'127 Hours': 5.0, 'Taken 3': 4.0, 'Avatar': 5.0, 'Nonstop': 3.0}}
Return 'similar score' based on two dictionaries' similarity in Python?