Transposes musical scales Pythonically!

scale_transpose.py

root_notes = [
    'A',
    'A#',
    'B',
    'C',
    'C#',
    'D',
    'D#',
    'E',
    'F',
    'F#',
    'G',
    'G#'
]

full = 2
half = 1

intervals = dict()
# Please add more intervals
intervals['major'] = [full, full, half, full, full, full, half]
intervals['natural_minor'] = [full, half, full, full, half, full, full]


def scalify(root, interval):
    root_number = root_notes.index(root)
    scale_intervals = intervals[interval]

    scale = [root_notes[root_number]]

    # deque from collections package would be more elegant
    for tone in scale_intervals:
        root_number += tone
        if root_number > 11:
            root_number -= 12
        scale.append(root_notes[root_number])

    return scale


def transpose(original, new, interval):
    original_scale = scalify(original, interval)
    new_scale = scalify(new, interval)

    return list(zip(original_scale, new_scale))


# Demo
d_to_c = transpose('D', 'C', 'major')
for o, n in d_to_c:
    print(f"{o:<2} -> {n}")