I have a logging function with hardcoded logfile name (LOG_FILE):
setup_logger.py
import logging
import sys
FORMATTER = logging.Formatter("%(levelname)s - %(asctime)s - %(name)s - %(message)s")
LOG_FILE = "my_app.log"
def get_console_handler():
console_handler = logging.StreamHandler(sys.stdout)
console_handler.setFormatter(FORMATTER)
return console_handler
def get_file_handler():
file_handler = logging.FileHandler(LOG_FILE)
file_handler.setFormatter(FORMATTER)
return file_handler
def get_logger(logger_name):
logger = logging.getLogger(logger_name)
logger.setLevel(logging.DEBUG) # better to have too much log than not enough
logger.addHandler(get_console_handler())
logger.addHandler(get_file_handler())
# with this pattern, it's rarely necessary to propagate the error up to parent
logger.propagate = False
return logger
I use this in various modules this way:
main.py
from _Core import setup_logger as log
def main(incoming_feed_id: int, type: str) -> None:
logger = log.get_logger(__name__)
...rest of my code
database.py
from _Core import setup_logger as log
logger = log.get_logger(__name__)
Class Database:
...rest of my code
etl.py
import _Core.database as db
from _Core import setup_logger as log
logger = log.get_logger(__name__)
Class ETL:
...rest of my code
What I want to achieve is to always change the logfile's path and name on each run based on arguments passed to the main() function in main.py.
Simplified example:
If main() receives the following arguments: incoming_feed_id = 1, type = simple_load, the logfile's name should be 1simple_load.log.
I am not sure what is the best practice for this. What I came up with is probably the worst thing to do: Add a log_file parameter to the get_logger() function in setup_logger.py, so I can add a filename in main() in main.py. But in this case I would need to pass the parameters from main to the other modules as well, which I do not think I should do as for example the database class is not even used in main.py.
I don't know enough about your application to be sure this'll work for you, but you can just configure the root logger in main() by calling get_logger('', filename_based_on_cmdline_args), and stuff logged to the other loggers will be passed to the root logger's handlers for processing if the logger levels configured allow it. The way you're doing it now seems to open multiple handlers pointing to the same file, which seems sub-optimal. The other modules can just use logging.getLogger(__name__) rather than log.get_logger(__name__).
Related
Is it possible for a library of code to obtain a reference to a logger object created by client code that uses a unique name?
The python advanced logging tutorial says the following:
A good convention to use when naming loggers is to use a module-level logger, in each module which uses logging, named as follows:
logger = logging.getLogger(__name__) This means that logger names track the package/module hierarchy, and it’s intuitively obvious where events are logged just from the logger name.
Every module in my library does:
LOG = logging.getLogger(__name__)
This works fine when client code does something like:
logger = logging.getLogger()
But breaks (I get no log output to the registered handlers from the logging object in main) when client code does something like:
logger = logging.getLogger('some.unique.path')
Because I am packaging my code as a library to be used with a lot of different clients, I want to have the most extensible logging. That is, I want my module level logging to reference the same logger object as main whenever possible, whether the client code is using a named logger or not.
Here is an example program to reproduce on your end. Imagine test.py is my library of code that I want to always reference any logger created in main.py.
Example Output
% python3 main.py
in main
%
Desired Output
% python3 main.py
in main
hi
%
main.py
import logging
from test import somefunc
LOG = logging.getLogger('some.unique.path')
LOG.setLevel(logging.DEBUG)
ch = logging.StreamHandler()
LOG.addHandler(ch)
def main():
LOG.info('in main')
somefunc()
if __name__ == '__main__':
main()
test.py
import logging
LOG = logging.getLogger(__name__)
def somefunc():
LOG.info('hi')
This is the approach I would take.
Create a separate logging utility. I have attached the code for it below.
Now, import this logger utility (or) class (or) function that this provides, wherever needed.
Updated your code, assuming I am using the above linked logger utility and tested it locally on my machine.
Code for main.py
from logger import get_logger
from test import somefunc
LOG = get_logger()
def main():
LOG.info("in main")
somefunc()
if __name__ == "__main__":
main()
Code for test.py
from logger import get_logger
LOG = get_logger()
def somefunc():
LOG.info("hi")
Code for logger.py - Attaching the code here too
import logging
from logging.handlers import RotatingFileHandler
bytes_type = bytes
unicode_type = str
basestring_type = str
DEFAULT_LOGGER = "default"
INTERNAL_LOGGER_ATTR = "internal"
CUSTOM_LOGLEVEL = "customloglevel"
logger = None
_loglevel = logging.DEBUG
_logfile = None
_formatter = None
def get_logger(
name=None,
logfile=None,
level=logging.DEBUG,
maxBytes=0,
backupCount=0,
fileLoglevel=None,
):
_logger = logging.getLogger(name or __name__)
_logger.propagate = False
_logger.setLevel(level)
# Reconfigure existing handlers
has_stream_handler = False
for handler in list(_logger.handlers):
if isinstance(handler, logging.StreamHandler):
has_stream_handler = True
if isinstance(handler, logging.FileHandler) and hasattr(
handler, INTERNAL_LOGGER_ATTR
):
# Internal FileHandler needs to be removed and re-setup to be able
# to set a new logfile.
_logger.removeHandler(handler)
continue
# reconfigure handler
handler.setLevel(level)
if not has_stream_handler:
stream_handler = logging.StreamHandler()
setattr(stream_handler, INTERNAL_LOGGER_ATTR, True)
stream_handler.setLevel(level)
_logger.addHandler(stream_handler)
if logfile:
rotating_filehandler = RotatingFileHandler(
filename=logfile, maxBytes=maxBytes, backupCount=backupCount
)
setattr(rotating_filehandler, INTERNAL_LOGGER_ATTR, True)
rotating_filehandler.setLevel(fileLoglevel or level)
_logger.addHandler(rotating_filehandler)
return _logger
def setup_default_logger(
logfile=None, level=logging.DEBUG, formatter=None, maxBytes=0, backupCount=0
):
global logger
logger = get_logger(
name=DEFAULT_LOGGER, logfile=logfile, level=level, formatter=formatter
)
return logger
def reset_default_logger():
"""
Resets the internal default logger to the initial configuration
"""
global logger
global _loglevel
global _logfile
global _formatter
_loglevel = logging.DEBUG
_logfile = None
_formatter = None
logger = get_logger(name=DEFAULT_LOGGER, logfile=_logfile, level=_loglevel)
# Initially setup the default logger
reset_default_logger()
def loglevel(level=logging.DEBUG, update_custom_handlers=False):
"""
Set the minimum loglevel for the default logger
Reconfigures only the internal handlers of the default logger (eg. stream and logfile).
Update the loglevel for custom handlers by using `update_custom_handlers=True`.
:param int level: Minimum logging-level (default: `logging.DEBUG`).
:param bool update_custom_handlers: custom handlers to this logger; set `update_custom_handlers` to `True`
"""
logger.setLevel(level)
# Reconfigure existing internal handlers
for handler in list(logger.handlers):
if hasattr(handler, INTERNAL_LOGGER_ATTR) or update_custom_handlers:
# Don't update the loglevel if this handler uses a custom one
if hasattr(handler, CUSTOM_LOGLEVEL):
continue
# Update the loglevel for all default handlers
handler.setLevel(level)
global _loglevel
_loglevel = level
def formatter(formatter, update_custom_handlers=False):
"""
Set the formatter for all handlers of the default logger
:param Formatter formatter: default uses the internal LogFormatter.
:param bool update_custom_handlers: custom handlers to this logger - set ``update_custom_handlers`` to `True`
"""
for handler in list(logger.handlers):
if hasattr(handler, INTERNAL_LOGGER_ATTR) or update_custom_handlers:
handler.setFormatter(formatter)
global _formatter
_formatter = formatter
def logfile(
filename,
formatter=None,
mode="a",
maxBytes=0,
backupCount=0,
encoding=None,
loglevel=None,
):
"""
Function to handle the rotating fileHandler
:param filename: filename logs are being collected
:param mode: fileMode
:param maxBytes: values for roll-over at a pre-determined size; if zero; rollover never occurs
:param backupCount: if value is non-zero; system saves old logfiles; by appending extensions
:param encoding: set encoding option; if not None; open file with that encoding.
:param loglevel: loglevel set
"""
# Step 1: If an internal RotatingFileHandler already exists, remove it
for handler in list(logger.handlers):
if isinstance(handler, RotatingFileHandler) and hasattr(
handler, INTERNAL_LOGGER_ATTR
):
logger.removeHandler(handler)
# Step 2: If wanted, add the RotatingFileHandler now
if filename:
rotating_filehandler = RotatingFileHandler(
filename,
mode=mode,
maxBytes=maxBytes,
backupCount=backupCount,
encoding=encoding,
)
# Set internal attributes on this handler
setattr(rotating_filehandler, INTERNAL_LOGGER_ATTR, True)
if loglevel:
setattr(rotating_filehandler, CUSTOM_LOGLEVEL, True)
# Configure the handler and add it to the logger
rotating_filehandler.setLevel(loglevel or _loglevel)
logger.addHandler(rotating_filehandler)
Output:
in main
hi
Note:
Do dive deep into the Logger Utility linked to understand all the internal details.
Use logging.basicConfig instead of manually trying to configure a logger. Loggers inherit their configuration from their parent.
import logging
from test import somefunc
LOG = logging.getLogger('some.unique.path')
def main():
LOG.info('in main')
somefunc()
if __name__ == '__main__':
logging.basicConfig(level=logging.DEBUG)
main()
I have a main process which makes use of different other modules. And these modules also use other modules. I need to log all the logs into single log file. Due to use of TimedRotatingFileHandler, my log behaves differently after midnight. I got to know why it so but couldn't clearly how I can solve it.
Below is log_config.py which is used by all other modules to get the logger and log.
'''
import logging
import sys
from logging.handlers import TimedRotatingFileHandler
FORMATTER = logging.Formatter("%(asctime)s — %(name)s — %(message)s")
LOG_FILE = "my_app.log"
def get_file_handler():
file_handler = TimedRotatingFileHandler(LOG_FILE, when='midnight')
file_handler.setFormatter(FORMATTER)
return file_handler
def get_logger(logger_name):
logger = logging.getLogger(logger_name)
logger.setLevel(logging.DEBUG) # better to have too much log than not enough
logger.addHandler(get_file_handler())
#with this pattern, it's rarely necessary to propagate the error up to parent
logger.propagate = False
return logger
'''
All other modules call,
'logging = log_config.get_logger(name)'
and use it to log.
I came to know about QueueHandler and QueueListener but not sure how to use them in my code.
How can I use these to serialize logs to single file.?
Is there any way I can provide the filename for logger from my main module?
I am using following way, however it's not working.all the logs go to xyz.log file rather than main.log
Updated as per suggestion from nosklo
logger.py
formatter = logging.Formatter(fmt='[%(asctime)s] - {%(filename)s:%(lineno)d} %(levelname)s - %(message)s')
def _get_file_handler(file_name="xyz.log"):
file_handler = logging.FileHandler(file_name)
file_handler.setLevel(logging.DEBUG)
file_handler.setFormatter(formatter)
return file_handler
def get_logger(name):
logger = logging.getLogger(name)
logger.setLevel(logging.DEBUG)
logger.addHandler(_get_file_handler())
return logger
parser.py
log = logger.get_logger(__name__)
def parse():
log.info("is there anyway this could go to main.log and xyz.log")
main.py
log = logger.get_logger(__name__)
if __name__ == '__main__':
for handler in log.handlers:
if isinstance(handler, logging.FileHandler):
log.removeHandler(handler)
log.addHandler(logger._get_file_handler())
log.info("is there anyway this could go to main.log and xyz.log?")
parser.parse()
Is there a way I can set the Log file name from my main.py module and not from logger.py module?
You're calling get_logger() first, so when you set the class attribute in FileName.file_name = "main.log" the get_logger function is already finished, and the logger is already defined to write in xyz.log; Changing the variable later won't change the logger anymore, since it is already defined.
To change the previously selected file, you'd have to retrieve the logger, remove the previous handler and add a new file handler. Another option is to set the variable before calling get_logger() so when you call it, the variable already has the correct value.
Logging instances can have multiple file handlers. Use a function like this to just add another handler with the additional output path you want. Log messages will get sent to both (or all) text logs added to the instance. You can even configure the handlers to have different logging levels so you can filter messages to different logs for critical errors, info message, etc.
import logging
def add_handler(output_log_path, log):
# Set up text logger and add it to logging instance
file_logger = logging.FileHandler(output_log_path)
file_logger.setLevel(logging.DEBUG)
formatter = logging.Formatter('%(asctime)s | logger name: %(name)s | module: %(module)s | lineno: %(lineno)d | %(message)s')
file_logger.setFormatter(formatter)
log.addHandler(file_logger)
return log
I have been writing simple scripts and I am trying to use logger to generate log for each functions in the scripts.
1) based on the function name I create a logger filehandler and I try to put logs using that handler. I also delete the previous existing file with the same name.
3) at the end of the function I close the handler.
My problem are:
1)even though I close the handler, the next time I run the same function I get an error that the file I am trying to delete is (as a part of setting the logger file handler) is still being used.
2) Also the logger prints everything to console which I dont want, I just want it to write everything to the file.
Here are the logger functions:
def setLogger(path):
"""
#purpose: Intializes basic logging directory and file
"""
LOG_FILENAME = path + "\\" + "log.txt"
#logging.basicConfig(filename=LOG_FILENAME,
# format='%(levelname)s %(asctime)s %(message)s',level=logging.INFO
# )
logger = logging.getLogger()
logger.setLevel(logging.INFO)
file_handler = logging.FileHandler(LOG_FILENAME)
file_handler.setLevel(logging.INFO)
formatter = logging.Formatter("%(levelname)s %(asctime)s %(message)s")
file_handler.setFormatter(formatter)
logger.addHandler(file_handler)
return logger
def unsetLogger(logger):
"""
#purpose: performs a basic shutdown of logger
"""
logger.handlers[0].close()
logger.removeHandler(logger.handlers[0])
logging.shutdown
The way i use them is:
for eg:
def fun():
os.remove(path)
logger = setLogger(path)
` logging.info("hi") #this writes to file and prints on the console as well
unsetLogger(logger)
if I run the function fun() once, its all good. but if i run it again, I get that can't delete error for the log file.
Thanks in Advance.
learningNinja
After making some slight modifications, I came up with the following test to try to reproduce your error, but I don't get any errors.
import os
import logging
def setLogger(path):
"""
#purpose: Intializes basic logging directory and file
"""
logger = logging.getLogger()
logger.setLevel(logging.INFO)
# Simplified log file path (I just use full value passed in, and don't append "\log.txt")
file_handler = logging.FileHandler(path)
file_handler.setLevel(logging.INFO)
formatter = logging.Formatter("%(levelname)s %(asctime)s %(message)s")
file_handler.setFormatter(formatter)
logger.addHandler(file_handler)
return logger
def unsetLogger(logger):
"""
#purpose: performs a basic shutdown of logger
"""
logger.handlers[0].close()
logger.removeHandler(logger.handlers[0])
logging.shutdown
def fun():
try:
# Was getting error trying to remove a file that didn't exist on
# first execution...
os.remove("log.txt")
except:
pass
logger = setLogger("log.txt")
logging.info("hi")
unsetLogger(logger)
fun()
fun()
fun()
See if there is anything I'm doing differently than your actual code and maybe that might help you.
I created a module named log.py where a function defines how the log will be registered. Here is the atomic code:
import logging
import time
def set_up_log():
"""
Create a logging file.
"""
#
# Create the parent logger.
#
logger = logging.getLogger(__name__)
logger.setLevel(logging.INFO)
#
# Create a file as handler.
#
file_handler = logging.FileHandler('report\\activity.log')
file_handler.setLevel(logging.INFO)
formatter = logging.Formatter('%(asctime)s - %(filename)s - %(name)s - % (levelname)4s - %(message)s')
file_handler.setFormatter(formatter)
logger.addHandler(file_handler)
#
# Start recording.
#
logger.info('______ STARTS RECORDING _______')
if __name__=='__main__':
set_up_log()
A second module named read_file.py is using this log.py to record potential error.
import logging
import log
log.set_up_log()
logger = logging.getLogger(__name__)
def read_bb_file(input_file):
"""
Input_file must be the path.
Open the source_name and read the content. Return the result.
"""
content = list()
logger.info('noi')
try:
file = open(input_file, 'r')
except IOError, e:
logger.error(e)
else:
for line in file:
str = line.rstrip('\n\r')
content.append(str)
file.close()
return content
if __name__ == "__main__":
logger.info("begin execution")
c = read_bb_file('textatraiter.out')
logger.info("end execution")
In the command prompt lauching read_file.py, I get this error:
No handlers could be found for logger "__main__"
My result in the file is the following
2014-05-12 13:32:58,690 - log.py - log - INFO - ______ STARTS RECORDING _______
I read lots of topics here and on Py Doc but it seems I did not understand them properly since I have this error.
I add I would like to keep the log settlement appart in a function and not define it explicitely in my main method.
You have 2 distinct loggers and you're only configuring one.
The first is the one you make in log.py and set up correctly. Its name however will be log, because you have imported this module from read_file.py.
The second logger, the one you're hoping is the same as the first, is the one you assign to the variable logger in read_file.py. Its name will be __main__ because you're calling this module from the command line. You're not configuring this logger.
What you could do is to add a parameter to set_up_log to pass the name of the logger in, e.g.
def set_up_log(logname):
logger = logging.getLogger(logname)
That way, you will set the handlers and formatters for the correct logging instance.
Organizing your logs in a hierarchy is the way logging was intended to be used by Vinay Sajip, the original author of the module. So your modules would only log to a logging instance with the fully qualified name, as given by __name__. Then your application code could set up the loggers, which is what you're trying to accomplish with your set_up_log function. You just need to remember to pass it the relevant name, that's all. I found this reference very useful at the time.