Print in multi-threaded/multi-process env

printflock.py

# from https://github.com/stas00/toolbox/blob/master/pytorch/all_reduce_bench.py

def printflock(*msgs):
    """ print """
    with open(__file__, "r") as fh:
        fcntl.flock(fh, fcntl.LOCK_EX)
        try:
            print(*msgs)
        finally:
            fcntl.flock(fh, fcntl.LOCK_UN)