python logging shows no sys.stdout when from different thread

Question

i now have a strange problem with logging in my multithreaded python application. Whenever i debug the application, i properly see the logging output in the stdout, such as

2016-11-05 21:51:36,851 (connectionpool.py:735 MainThread) INFO -     requests.packages.urllib3.connectionpool: "Starting new HTTPS connection (1): api.telegram.org"
2016-11-05 21:51:41,920 (converter.py:16 WorkerThread1) DEBUG - converter: "resizing file test/test_input/"
2016-11-05 21:51:50,199 (bot.py:221 WorkerThread1) ERROR - __main__: "MoviePy error: failed to read the duration of file test/test_input/. 

However, when i run the code without debug, all the logs from the WorkingThread1 disappear, leaving only the MainThread ones. The code is unchanged and the error remains. I guess it has something to do with multithreading. The WorkerThread1 is started from the pyTelegramBotAPI framework. I have my logs output to the sys.stdout :

formatter = logging.Formatter(
    '%(asctime)s (%(filename)s:%(lineno)d %(threadName)s) %(levelname)s - %(name)s: "%(message)s"')
stream_handler = logging.StreamHandler(sys.stdout)
stream_handler.setFormatter(formatter)
root = logging.getLogger()
root.setLevel(logging.NOTSET)
root.addHandler(stream_handler)

Any ideas?

Update : it has 100% to do with multithreading, because when i tell the framework to only use one thread, the logging messages appear. pyTelegramBotAPI uses WorkerThread and ThreadPool to implement concurrency as exemplified here

Answer 1

You have to show more code. In the code which you have shown, stream_handler is created, but then handler is used in addHandler .

My guess will be that your logging level is improperly set causing all the logs from the WorkingThread1 to be not logged.