import os, threading

file = open('logthred.log', 'a')

lock = threading.RLock()

class IOThread(threading.Thread):
    def __init__(self, numLoops, n):
        threading.Thread.__init__(self)
        self.name = 'thread-%02d' % n
        self.numLoops = numLoops

    def run(self):
        global file
        for x in range(0, self.numLoops):
            os.system('cd . > blah.txt')
            os.system('del blah.txt')
            s = 'This is log message ' + str(x) + ' from ' + self.name + ' and I think this should be a little longer, so I\'ll add some more data here because perhaps the size of the individual log message is a factor.  Who knows for sure until this simple test fails.'
            lock.acquire()
            try:
                if file.tell() + len(s) < 2048:
                    print >> file, s
                else:
                    file.close()
                    dfn = 'logthred.log.1'
                    if os.path.exists(dfn):
                        os.remove(dfn)
                    os.rename('logthred.log', dfn)
                    file = open('logthred.log', 'a')
            finally:
                lock.release()

if __name__=="__main__":
    numThreads = 10
    numLoops = 100

    # Create and execute threads
    threads = []
    for x in range(0, numThreads):
        t = IOThread(numLoops, x)
        print t.name
        threads.append(t)
        t.start()
    for t in threads:
        print "Joining", t.name
        t.join()