NES Game Genie code generator

nesggcc.py

#!/usr/bin/python

# This python script will generate game genie codes for NES
# Pass in the address and value, with an optional compare value
# in hexadecimal format and it will output a game genie code.
# This is quick and dirty and largely untested, so YMMV.

from sys import argv

if len(argv) < 3:
    print(f'Usage: {argv[0]} <address> <value> [<compare>]')
    print("All values should be in hexadecimal")
    exit(-1)

letters = 'APZLGITYEOXUKSVN'

bit_order_6 = '1678H234:IJKLABCDMNO5EFG'
bit_order_8 = '1678H234:IJKLABCDMNOwEFGsxyz5tuv'

address = int(argv[1], 16) # between 0x8000 and 0xffff
value = int(argv[2], 16) # between 0x0 and 0xff

bit_order = bit_order_6
addr_int = ((value << 16) | (address)) & 0x7fff
if len(argv) > 3:
    compare = int(argv[3], 16) # between 0x0 and 0xff
    bit_order = bit_order_8
    addr_int |= 0x1000
    addr_int = (addr_int << 8) | (compare)
sorted_bit_order = sorted(bit_order)

code_int = 0
for i,v in  enumerate(bit_order):
    code_int <<= 1
    bit_index = sorted_bit_order.index(v)
    code_int |= (addr_int >> (len(bit_order) - 1 - bit_index) & 1)

gg_code = ''
for i in range(len(bit_order) - 4, -1, -4):
    gg_code += letters[(code_int >> i) & 0xf]

print(gg_code)