Python logging not outputting anything

Question

In a python script I am writing  I am trying to log events using the logging module  I have the following code to configure my logger   ERROR FORMAT      levelname s at   asctime s in   funcName s in   filename  at line   lineno d    message s  DEBUG FORMAT      lineno d in   filename s at   asctime s    message s  LOG CONFIG     version  1                 formatters    error    format  ERROR FORMAT                                debug    format  DEBUG FORMAT                   handlers    console    class   logging StreamHandler                                         formatter   debug                                         level  logging DEBUG                              file    class   logging FileHandler                                      filename    usr local logs DatabaseUpdate log                                      formatter   error                                      level  logging ERROR                   root    handlers    console    file     logging config dictConfig LOG CONFIG    When I try to run logging debug  Some string    I get no output to the console  even though this page in the docs says that logging debug should have the root logger output the message  Why is my program not outputting anything  and how can I fix it

User · Answer

Many years later there seems to still be a usability problem with the Python logger. Here's some explanations with examples:

import logging
# This sets the root logger to write to stdout (your console).
# Your script/app needs to call this somewhere at least once.
logging.basicConfig()

# By default the root logger is set to WARNING and all loggers you define
# inherit that value. Here we set the root logger to NOTSET. This logging
# level is automatically inherited by all existing and new sub-loggers
# that do not set a less verbose level.
logging.root.setLevel(logging.NOTSET)

# The following line sets the root logger level as well.
# It's equivalent to both previous statements combined:
logging.basicConfig(level=logging.NOTSET)


# You can either share the `logger` object between all your files or the
# name handle (here `my-app`) and call `logging.getLogger` with it.
# The result is the same.
handle = "my-app"
logger1 = logging.getLogger(handle)
logger2 = logging.getLogger(handle)
# logger1 and logger2 point to the same object:
# (logger1 is logger2) == True


# Convenient methods in order of verbosity from highest to lowest
logger.debug("this will get printed")
logger.info("this will get printed")
logger.warning("this will get printed")
logger.error("this will get printed")
logger.critical("this will get printed")


# In large applications where you would like more control over the logging,
# create sub-loggers from your main application logger.
component_logger = logger.getChild("component-a")
component_logger.info("this will get printed with the prefix `my-app.component-a`")

# If you wish to control the logging levels, you can set the level anywhere 
# in the hierarchy:
#
# - root
#   - my-app
#     - component-a
#

# Example for development:
logger.setLevel(logging.DEBUG)

# If that prints too much, enable debug printing only for your component:
component_logger.setLevel(logging.DEBUG)


# For production you rather want:
logger.setLevel(logging.WARNING)

A common source of confusion comes from a badly initialised root logger. Consider this:

import logging
log = logging.getLogger("myapp")
log.warning("woot")
logging.basicConfig()
log.warning("woot")

Output:

woot
WARNING:myapp:woot

Depending on your runtime environment and logging levels, the first log line (before basic config) might not show up anywhere.

User · Answer

Maybe try this  It seems the problem is solved after remove all the handlers in my case   for handler in logging root handlers         logging root removeHandler handler   logging basicConfig filename  output log   level logging INFO

User · Answer

The default logging level is warning  Since you haven t changed the level  the root logger s level is still warning  That means that it will ignore any logging with a level that is lower than warning  including debug loggings   This is explained in the tutorial   import logging logging warning  Watch out      will print a message to the console logging info  I told you so     will not print anything   The  info  line doesn t print anything  because the level is higher than info   To change the level  just set it in the root logger    root    handlers    console    file     level   DEBUG     In other words  it s not enough to define a handler with level DEBUG  the actual logging level must also be DEBUG in order to get it to output anything

User · Answer

For anyone here that wants a super-simple answer  just set the level you want displayed  At the top of all my scripts I just put   import logging logging basicConfig level   logging INFO    Then to display anything at or above that level   logging info  Hi you just set your fleeb to level plumbus     It is a hierarchical set of five levels so that logs will display at the level you set  or higher  So if you want to display an error you could use logging error  The plumbus is broken     The levels  in increasing order of severity  are DEBUG  INFO  WARNING  ERROR  and CRITICAL  The default setting is WARNING    This is a good article containing this information expressed better than my answer  https   www digitalocean com community tutorials how-to-use-logging-in-python-3

[python] Python logging not outputting anything

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