tuple-of-tuples - find the class wise roll number

Find the class wise roll number from a tuple-of-tuples.
Expected output:
defaultdict(, {‘VII’: [1], ‘V’: [1, 2], ‘VI’: [1, 2, 3]})
from collections import defaultdict

classes = (
    ('V', 1),
    ('VI', 1),
    ('V', 2),
    ('VI', 2),
    ('VI', 3),
    ('VII', 1),
)

class_rollno = defaultdict(list)

for class_name, roll_id in classes:
    class_rollno[class_name].append(roll_id)

print(class_rollno)

Output:

defaultdict(<class 'list'>, {'VII': [1], 'VI': [1, 2, 3], 'V': [1, 2]})