import struct, fcntl
def writelock(f):
_lock(f, fcntl.F_WRLCK)
def readlock(f):
_lock(f, fcntl.F_RDLCK)
def unlock(f):
_lock(f, fcntl.F_UNLCK)
def _lock(f, op):
dummy = fcntl.fcntl(f.fileno(), fcntl.F_SETLKW,
struct.pack('2h8l', op,
0, 0, 0, 0, 0, 0, 0, 0, 0))