Implementation of PPM filename checksum used when Flipnotes are saved into storage

ppm_filename_checksum.py

checksum_dict = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ'

def calc_check_digit(filename):
  sumc = int(filename[0:2], 16)
  for i in range(1, 16):
    char = ord(filename[i])
    sumc = (sumc + char) % 256
  return checksum_dict[sumc % len(checksum_dict)]

def set_check_digit(filename):
  digit = calc_check_digit(filename)
  filename = digit + filename[1:]
  return filename

# Example
set_check_digit('F78DA8_14768882B56B8_030')