Sonic and Knuckles Lock-on Builder

import os
import sys

def buildRom(bname,fname):
    name,ext=os.path.splitext(os.path.basename(fname))

    # Read Sonic & Knuckles data.
    f=open("%s.md" % bname,"rb")
    data1=f.read()
    f.close()

    # Open locked-on ROM.
    f=open(fname,"rb")

    # Get file size.
    f.seek(0x00,2)
    size=f.tell()

    if size<0x200:
        print("Not a Genesis/Mega Drive ROM")
        return False

    f.seek(0x100)
    testData=f.read(0x10)
    if testData not in [b"SEGA MEGA DRIVE ",b"SEGA GENESIS    "]:
        print("Not a Genesis/Mega Drive ROM")
        return False

    # Round the size up to the next power of two to get the true ROM size.
    romSize=1<<(size-1).bit_length()

    # Append the last 2 MiB from locked-on ROM.
    f.seek(max(0x00,romSize-0x200000))
    data2=f.read()
    f.close()

    # Check if it's Sonic 2 and append 256 KiB patch ROM if needed.
    isSonic2=False

    # Lock-on serials:
    # "GM 00001051-00" # Sonic 2 REV00
    # "GM 00001051-01" # Sonic 2 REV01
    # "GM 00001051-02" # Sonic 2 REV02
    # "GM MK-1079 -00" # Sonic 3
    # Blue Spheres unlocking serials:
    # "GM 00001009-0" # Sonic 1 REV00
    # "GM 00004049-0" # Sonic 1 REV01
    if (data2[0x180:0x18e] in [b"GM 00001051-00",b"GM 00001051-01",b"GM 00001051-02"]):
        isSonic2=True
        f=open("Sonic & Knuckles (World) (Lock-on).bin","rb")
        datas2k=f.read()
        f.close()

    f=open("%s + %s.md" % (bname,name),"wb")
    f.write(data1)
    f.write(data2)
    if isSonic2: f.write(datas2k)
    f.close()

    return True

if __name__=="__main__":
    bname="Sonic & Knuckles (World)"
    fname=sys.argv[1]
    buildRom(bname,fname)