Simple indexing into a list or iterable by name

multi_index.py

def build_index(*fields):
    '''each arg is (field_name, length) tuple'''
    index = type('Index', (object,), {})
    start = 0
    for field, offset in fields:
        s = slice(start, start + offset)
        setattr(index, field, s)
        start += offset
    return index


#=========
# Sample usage
#=========

r = range(30)
fields = [
    ('first', 3),
    ('second', 5),
    ('third', 6)
]

index = build_index(*fields)
print(r[index.first])  # [0, 1, 2]
print(r[index.second]) # [3, 4, 5, 6, 7]
print(r[index.third])  # [8, 9, 10, 11, 12, 13]