A Python script to convert Game Boy memory addresses between absolute and banked forms.

banksy.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

# Convert Game Boy addresses between absolute and banked forms.

from __future__ import print_function
from __future__ import unicode_literals

import sys

def to_banked(absolute_address):
    absolute_address = int(absolute_address, 16)
    bank, address = absolute_address // 0x4000, absolute_address % 0x4000
    if bank != 0:
        address += 0x4000
    return "{:02X}:{:04X}".format(bank, address)

def to_absolute(banked_address):
    bank, address = [int(n, 16) for n in banked_address.split(':', 1)]
    
    memory_start = 0 if bank == 0 else 0x4000
    if not memory_start <= address < memory_start + 0x4000:
        raise ValueError("Memory address not within bank.")
    
    return "{:06X}".format(bank * 0x4000 + address - memory_start)

def cross_convert(address):
    if ':' in address:
        return to_absolute(address)
    else:
        return to_banked(address)

if __name__ == '__main__':
    if not sys.argv[1:]:
        print("Usage: banksy [addresses...]")
        print("For example: banksy BC160 6F:430A")
    else:
        for address in sys.argv[1:]:
            try:
                print(cross_convert(address))
            except ValueError:
                print("[invalid address]")