log.py

# logging
#
# One can simply use
# import log
# print("Some text", file=log)
# because the log unit looks enough like a file!
import sys
import threading
from six.moves import cStringIO as StringIO


logfile = StringIO()
# Need to make our operations thread-safe.
mutex = threading.Lock()


def write(data):
    mutex.acquire()
    try:
        if logfile.tell() > 2000:
            # Do a sort of 2k round robin
            logfile.seek(0)
        logfile.write(data)
    finally:
        mutex.release()
    sys.stdout.write(data)


def getvalue():
    mutex.acquire()
    try:
        pos = logfile.tell()
        head = logfile.read()
        logfile.seek(0)
        tail = logfile.read(pos)
    finally:
        mutex.release()
    return head + tail