Python: Stream Handler

By using Stream handler, you can send log records to a stream. Following program defines a stream handler that writes log records to standard output.

import logging
import sys

#Define logger
logger = logging.getLogger(__name__)
logging.basicConfig(level=logging.DEBUG, format='%(asctime)s %(name)-12s %(levelname)-8s %(message)s')

#Define handler to write to standard output
handler = logging.StreamHandler(sys.stdout)
formatter = logging.Formatter('[%(levelname)s] %(message)s')
handler.setFormatter(formatter)
handler.setLevel(logging.WARN)

#Adding handler to logger
logger.addHandler(handler)

def logMessages():
    logger.debug("Debug message")
    logger.info("Information Message")
    logger.warn("Warning Message")
    logger.error("Error Message")
    logger.critical("Critical Message")

if(__name__=="__main__"):
    logMessages()

Run above program, you will get following output.

2015-10-23 10:19:12,176 __main__     DEBUG    Debug message
[WARNING] Warning Message
[ERROR] Error Message
2015-10-23 10:19:12,176 __main__     INFO     Information Message
[CRITICAL] Critical Message
2015-10-23 10:19:12,177 __main__     WARNING  Warning Message
2015-10-23 10:19:12,177 __main__     ERROR    Error Message
2015-10-23 10:19:12,177 __main__     CRITICAL Critical Message

We set the log level WARN to the handler, so handler only logs Warning, Error, Critical messages.

StreamHandler provides following methods.

Method	Description
emit(record)	If formatter is specified, it is used to format the record.
flush()	Flush the stream.

        

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