How to write to a file using the logging Python module

Question

How can I use the logging module in Python to write to a file  Every time I try to use it  it just prints out the message

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Here is two examples  one print the logs  stdout  the other write the logs to a file  import logging import sys  logger   logging getLogger   logger setLevel logging INFO  formatter   logging Formatter    asctime s     levelname s     message s    stdout handler   logging StreamHandler sys stdout  stdout handler setLevel logging DEBUG  stdout handler setFormatter formatter   file handler   logging FileHandler  logs log   file handler setLevel logging DEBUG  file handler setFormatter formatter    logger addHandler file handler  logger addHandler stdout handler   With this example  all logs will be printed and also be written to a file named logs log Use example  logger info  This is a log message    logger error  This is an error message

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here s a simpler way to go about it  this solution doesn t use a  config dictionary and uses a rotation file handler  like so   import logging from logging handlers import RotatingFileHandler  logging basicConfig handlers  RotatingFileHandler filename logpath filename                       mode  w   maxBytes 512000  backupCount 4    level debug level                       format    levelname s   asctime s   message s                        datefmt   m  d  Y I  M  S  p    logger   logging getLogger  my logger     or like so   import logging from logging handlers import RotatingFileHandler  handlers                 RotatingFileHandler filename logpath filename  mode  w   maxBytes 512000                                   backupCount 4               logging basicConfig handlers handlers  level debug level                       format    levelname s   asctime s   message s                        datefmt   m  d  Y I  M  S  p    logger   logging getLogger  my logger     the handlers variable needs to be an iterable  logpath filename and debug level are just variables holding the  respective info  of course  the values for the function params are up  to you   the first time i was using the logging module i made the mistake of writing the following  which generates an OS file lock error  the above is the solution to that    import logging from logging handlers import RotatingFileHandler  logging basicConfig filename logpath filename  level debug level  format    levelname s   asctime s   message s   datefmt   m  d  Y   I  M  S  p    logger   logging getLogger  my logger   logger addHandler RotatingFileHandler filename logpath filename  mode  w                      maxBytes 512000  backupCount 4     and Bob s your uncle

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This example should work fine  I have added streamhandler for console   Console   log and file handler data should be similar          MUTHUKUMAR TIME DATE py   gt  gt  gt  gt  gt  gt  gt  gt  file name module       import sys     import logging     import logging config                          Logger                                      def Logger file name           formatter   logging Formatter fmt    asctime s   module s line    lineno d   levelname 8s     message s                                         datefmt   Y  m  d  H  M  S      I  M  S  p AM PM format         logging basicConfig filename     s log    file name  format     asctime s   module s line    lineno d   levelname 8s     message s                                         datefmt   Y  m  d  H  M  S   filemode    w   level   logging INFO          log obj   logging getLogger           log obj setLevel logging DEBUG            log obj   logging getLogger   addHandler logging StreamHandler               console printer         screen handler   logging StreamHandler stream sys stdout   stream sys stdout is similar to normal print         screen handler setFormatter formatter          logging getLogger   addHandler screen handler           log obj info  Logger object created successfully             return log obj                                                                 MUTHUKUMAR LOGGING CHECK py   gt  gt  gt  gt  gt  gt  gt  gt  gt  gt  gt  file name   calling   Logger   function file name    muthu  log obj  Logger file name  log obj info  yes   hfghghg ghgfh  format    log obj critical  CRIC  format    log obj error  ERR  format    log obj warning  WARN  format    log obj debug  debug  format    log obj info  qwerty  format    log obj info  asdfghjkl  format    log obj info  zxcvbnm  format      closing file log obj handlers clear    OUTPUT  2019 07 13 23 54 40 MUTHUKUMAR TIME DATE line  17     INFO   Logger object created successfully   2019 07 13 23 54 40 MUTHUKUMAR LOGGING CHECK line  8     INFO   yes   hfghghg ghgfh 2019 07 13 23 54 40 MUTHUKUMAR LOGGING CHECK line  9 CRITICAL   CRIC 2019 07 13 23 54 40 MUTHUKUMAR LOGGING CHECK line  10    ERROR   ERR 2019 07 13 23 54 40 MUTHUKUMAR LOGGING CHECK line  11  WARNING   WARN 2019 07 13 23 54 40 MUTHUKUMAR LOGGING CHECK line  12    DEBUG   debug 2019 07 13 23 54 40 MUTHUKUMAR LOGGING CHECK line  13     INFO   qwerty 2019 07 13 23 54 40 MUTHUKUMAR LOGGING CHECK line  14     INFO   asdfghjkl 2019 07 13 23 54 40 MUTHUKUMAR LOGGING CHECK line  15     INFO   zxcvbnm  Thanks

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import sys import logging  from util import reducer logfile logging basicConfig filename reducer logfile  format    message s                       level logging INFO  filemode  w

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Taken from the  logging cookbook      create logger with  spam application  logger   logging getLogger  spam application   logger setLevel logging DEBUG    create file handler which logs even debug messages fh   logging FileHandler  spam log   fh setLevel logging DEBUG  logger addHandler fh    And you re good to go   P S  Make sure to read the logging HOWTO as well

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http   docs python org library logging html logging basicConfig  logging basicConfig filename   path to your log   level

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I prefer to use a configuration file  It allows me to switch logging levels  locations  etc without changing code when I go from development to release  I simply package a different config file with the same name  and with the same defined loggers   import logging config if   name         main           Configure the logger       loggerConfigFileName  The name and path of your configuration file     logging config fileConfig path normpath loggerConfigFileName          Create the logger       Admin Client  The name of a logger defined in the config file     mylogger   logging getLogger  Admin Client        msg  Bite Me      myLogger debug msg      myLogger info msg      myLogger warn msg      myLogger error msg      myLogger critical msg         Shut down the logger     logging shutdown     Here is my code for the log config file   These are the loggers that are available from the code  Each logger requires a handler  but can have more than one  loggers  keys root Admin Client    Each handler requires a single formatter  handlers  keys fileHandler  consoleHandler    formatters  keys logFormatter  consoleFormatter    logger root  level DEBUG handlers fileHandler    logger Admin Client  level DEBUG handlers fileHandler  consoleHandler qualname Admin Client  propagate 0 Does not pass messages to ancestor loggers root  propagate 0     Do not use a console logger when running scripts from a bat file without a console   because it hangs   handler consoleHandler  class StreamHandler level DEBUG formatter consoleFormatter args  sys stdout    The comma is correct  because the parser is looking for args    handler fileHandler  class FileHandler level DEBUG formatter logFormatter   This causes a new file to be created for each script   Change time strftime   Y m d H M S   to time strftime   Y m d     And only one log per day will be created  All messages will be amended to it  args   D   Logs  PyLogs      time strftime   Y m d H M S     log    a      formatter logFormatter   name is the name of the logger root or Admin Client  levelname is the log message level debug  warn  ect   lineno is the line number from where the call to log is made  04d is simple formatting to ensure there are four numeric places with leading zeros  4s would work as well  but would simply pad the string with leading spaces  right justify  -4s would work as well  but would simply pad the string with trailing spaces  left justify  filename is the file name from where the call to log is made  funcName is the method name from where the call to log is made  format   asctime s     lineno d     message s  format   asctime s     name s     levelname s     message s  format   asctime s     name s     module s-  lineno      levelname s     message s  format   asctime s     name s     module s-  lineno 04d     levelname s     message s  format   asctime s     name s     module s-  lineno 4s     levelname -8s     message s  format   asctime s     levelname -8s     lineno 04d     message s    Use a separate formatter for the console if you want  formatter consoleFormatter  format   asctime s     levelname -8s     filename s-  funcName s-  lineno 04d     message s

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http   docs python org library logging handlers html filehandler     The FileHandler class  located in the core logging package  sends logging output to a disk file

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An example of using logging basicConfig rather than logging fileHandler    logging basicConfig filename logname                              filemode  a                               format    asctime s   msecs d   name s   levelname s   message s                               datefmt   H  M  S                               level logging DEBUG   logging info  Running Urban Planning    self logger   logging getLogger  urbanGUI     In order  the five parts do the following     set the output file  filename logname  set it to append rather than overwrite  filemode  a   determine the format of the output message  format      determine the format of the output time  datefmt   H  M  S   and determine the minimum message level it will accept  level logging DEBUG

[python] How to write to a file, using the logging Python module?

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