@Error

>>> len(ALPHABET)
63

But BASF64 requires a 64 element long alphabet.

>>> basf64_encode_group(b'\xff\xff\xff')
Traceback (most recent call last):
[…]
File "<python-input-2>", line 35, in basf64_encode_group
encoded += ALPHABET[sextet]
~~~~~~~~^^^^^^^^
IndexError: list index out of range