create multiple log files python

Question

I want to save my results as a log file, so I am thinking to import logging module. I understand that to output a file, the code is very straightforward.

logging.basicConfig(filename='logger.log', level=logging.INFO)
logging.debug('debug message')
logging.info('info message')
logging.warn('warn message')
logging.error('error message')
logging.critical('critical message')

However, what if I want to output multiple log files? for example, in the following for loop, each iteration will output a log file, how should I do this?

for i in range(1,10):
  print (i)
  #output a log file to save I value

I tried to use these code, but it's not working.

for i in range(1,10):
    filename = str.format('mylog%d.txt' % i)
    logging.basicConfig(format=log_fmt, level=logging.DEBUG, filename=filename)

    logging.debug('This is debug message')
    logging.info('This is info message')
    logging.warning('This is warning message')

Refer this Logging to two files with different settings

user20144392
– user20144392

2022-10-02 17:03:29 +00:00
Commented Oct 2, 2022 at 17:03 — user20144392
– user20144392, Commented Oct 2, 2022 at 17:03

wpercy · Accepted Answer · 2017-11-09 18:02:26Z

1

You're using the format function of strings incorrectly. You're trying to use string interpolation, which is an entirely different method of formatting strings. You should try something like this:

filename = 'mylog{0}.txt'.format(i)

The {0} explicitly states that you should take the first value passed to format. You could leave it as {} if you'd like - it makes no real difference.

answered Nov 9, 2017 at 18:02

wpercy

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1 Comment

HAO CHEN Over a year ago

thx, but still, it only create one log file, and all the results are showing in this single file.

Some · Accepted Answer · 2017-11-09 18:47:00Z

About file name:

filename = str.format('mylog%d.txt' % i)

is equal to:

filename = 'mylog%d.txt' % i

For output to multiple files you can use multiple handlers.

Logging class that handle logging.

root_logger = logging.getLogger()

Return you root handler. You can add or remove handlers to logger.

root_logger.handlers

Contains list of handlers of root logger.

first = root_logger.handlers[0]
first.close()
root_logger.removeHandler(first)

remove first handler.

new_handler = logging.FileHandler(file_name)
formatter = logging.Formatter('%(asctime)s ' + ' %(message)s', '%H:%M:%S')
new_handler.setFormatter(formatter)
root_logger.addHandler(new_handler)

Add new formatter to root_handler. You can output log to any files at the same time.

For more info read:

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