import os class FileLock: def __init__(self, filename): self.filename = filename self.fd = None = os.getpid() def acquire(self): try: self.fd =, os.O_CREAT|os.O_EXCL|os.O_RDWR) # Only needed to let readers know who's locked the file os.write(self.fd, "%d" % return 1 # return ints so this can be used in older Pythons except OSError: self.fd = None return 0 def release(self): if not self.fd: return 0 try: os.close(self.fd) os.remove(self.filename) return 1 except OSError: return 0 def __del__(self): self.release() def main(): lock = FileLock("lock.file") while 1: if lock.acquire(): raw_input("acquired lock. Press ENTER to release:") lock.release() raw_input("released lock. Press ENTER to retry:") else: raw_input("Unable to acquire lock. Press ENTER to retry:") if __name__ == "__main__": main()