Logging between classes in python

Question

I have three classes in python and they run in different threads. I would like to have output to the same file from all classes. Right now I created output method in main class and passing it through constructors to other classes. Is there way to handle it better? How I can pass the logger between classes except using contructors?

Perhaps python supports something like static method in Java, so I can write like Logger.info(message) in all three classes?

Another way probably could be redirecting global sys.stdout to the file, i.e specifying

logger = open('debug.txt', 'w')
sys.stdout = logger

Then using calls sys.stdout in all classes.

What do you think?

Answer 1

import logging
log = logging.getLogger("mylog")
log.setLevel(logging.DEBUG)

formatter = logging.Formatter(
    "%(asctime)s %(threadName)-11s %(levelname)-10s %(message)s")
# Alternative formatting available on python 3.2+:
# formatter = logging.Formatter(
#     "{asctime} {threadName:>11} {levelname} {message}", style='{')

# Log to file
filehandler = logging.FileHandler("debug.txt", "w")
filehandler.setLevel(logging.DEBUG)
filehandler.setFormatter(formatter)
log.addHandler(filehandler)

# Log to stdout too
streamhandler = logging.StreamHandler()
streamhandler.setLevel(logging.INFO)
streamhandler.setFormatter(formatter)
log.addHandler(streamhandler)

# Test it
log.debug("Some message")
log.error("An error!")
try:
    something()
except:
    log.exception("An exception occured!")

And get in debug.txt:

2011-01-18 12:07:24,943  MainThread  DEBUG      Some message
2011-01-18 12:07:24,943  MainThread  ERROR      An error!
2011-01-18 12:07:24,943  MainThread  ERROR      An exception occured!
Traceback (most recent call last):
  File "./logtest.py", line 17, in 
    something()
NameError: name 'something' is not defined

Note that the order in which the messages appear in the log file may not correspond exactly to the order in which they happened when you're logging from several threads.