Using the python logging package, and writing a class Log, I’d like to tee stdout and stderr to a log file :
log = Log("log.txt") print "line1" print "line2" print >>sys.stderr, "err1" del log print "line to screen only"
The output log file would contain :
16/11/2017 09:51:58 INFO - line1 16/11/2017 09:51:58 INFO - line2 16/11/2017 09:51:58 INFO - err1
Any idea how to write this Log class, keeping the advantages of the “logging” package (time-stamps, …) ?
The right way to achieve what you ask is to use Logger object. It gives you much more flexability. This object can be bound to multiple handlers; You need a streamhandler to log message to
sys.stdout and a file handler to log it to a file. You then both print to the screen and log to a file in a single command.
import logging # create logger logger = logging.getLogger('example') logger.setLevel(logging.INFO) # create file handler which logs messages fh = logging.FileHandler('fh.log') fh.setLevel(logging.DEBUG) # create console handler to print to screen ch = logging.StreamHandler() ch.setLevel(logging.INFO) # create formatter and add it to the handlers formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s') fh.setFormatter(formatter) ch.setFormatter(formatter) # add the handlers to the logger logger.addHandler(fh) logger.addHandler(ch)
Now every call to
logger.info(msg) will be printed both to the screen, and written to
There is another way, where you can replace
sys.stderr stream objects. Create a class and customize it (original answer here):
import sys class writer(object): _fh = None _orig_stdout = sys.stdout def __init__(self): _fh = open('logging.log', 'w') def write(self, data): fp.write(data) _orig_stdout.write(data) def flush(): _orig_stdout.flush() logger = writer() sys.stdout = logger sys.stderr = logger
I made this package to do exactly what you said.
pip install stdlogging
After installed from pip, you can capture any output by logging. But be careful to capture stdout because it’s very fragile.
import stdlogging stdlogging.enable(stdout=False, stderror=True)