GBD client in python

import os
import mmap
import struct

fmt = "=iii"

f = os.open("/dev/shm/gbd", os.O_RDWR | os.O_CREAT, 0o666)
#m = mmap.mmap(f, 0)
m = mmap.mmap(f, 0)
size = struct.calcsize(fmt)
global beat
beat = (0, 0, 0)
def run():
        global beat
        while True:
                b = m.read(size)
                m.seek(0)
                b = struct.unpack(fmt, b)
                if b != beat:
                        print(b)
                        beat = b
try:
    run()
except:
    print("exiting")
    m.close()
    #f.close()