def from_digits(digits, base):

return sum(n * base ** i for i, n in enumerate(reversed(digits)))

def to_digits(number, base_to):

result = []

while number > 0:

result.append(number % base_to)

number //= base_to

if result:

return result[::-1] # list(reversed(result))

return [0]

def rebase(from_base, digits, to_base):

if from_base < 2:

raise ValueError("Invalid input base.")

if to_base < 2:

raise ValueError("Invalid output base.")

if any(True for d in digits if d < 0 or d >= from_base):

raise ValueError("Invalid input digit.")

return to_digits(from_digits(digits, from_base), to_base)