Double or halve stepchart BPM

bpmtools.py

def to_pairs(xs):
    seq = iter(xs)
    while True:
        try:
            x = next(seq)
        except StopIteration:
            return
        try:
            y = next(seq)
        except StopIteration:
            yield (x, None)
            return
 
        yield (x, y)


def dilute_measure(m, new_length):
    if (new_length % len(m)) != 0:
        raise Exception(f"can't dilute {len(m)} to {new_length}")
    add_bars = new_length // len(m) - 1
    return sum(map(list, zip(m, *(repeat("0000") for _ in range(add_bars)))), [])


def lcm(x, y): 
    return (x * y) // gcd(x, y)


def join_measures(m, n):
    new_length = lcm(len(m), len(n))
    return dilute_measure(m, new_length) + dilute_measure(n, new_length)


def halve_bpm(measures):
    return [join_measures(a, b) for a, b in to_pairs(measures)]


def double_bpm(measures):
    return sum(([m[:len(m)//2], m[len(m)//2:]] for m in measures), [])


def notes_loads(notes):
    return [m.strip().split("\n") for m in notes.split(",")]


def notes_dumps(measures):
    return "\n,".join("\n".join(m) for m in measures)