How to Customize the time format for Python logging?

I am new to Python's logging package and plan to use it for my project. I would like to customize the time format to my taste. Here is a short code I copied from a tutorial:

import logging

# create logger
logger = logging.getLogger("logging_tryout2")
logger.setLevel(logging.DEBUG)

# create console handler and set level to debug
ch = logging.StreamHandler()
ch.setLevel(logging.DEBUG)

# create formatter
formatter = logging.Formatter("%(asctime)s;%(levelname)s;%(message)s")

# add formatter to ch
ch.setFormatter(formatter)

# add ch to logger
logger.addHandler(ch)

# "application" code
logger.debug("debug message")
logger.info("info message")
logger.warn("warn message")
logger.error("error message")
logger.critical("critical message")

And here is the output:

2010-07-10 10:46:28,811;DEBUG;debug message
2010-07-10 10:46:28,812;INFO;info message
2010-07-10 10:46:28,812;WARNING;warn message
2010-07-10 10:46:28,812;ERROR;error message
2010-07-10 10:46:28,813;CRITICAL;critical message

I would like to shorten the time format to just: '2010-07-10 10:46:28', dropping the mili-second suffix. I looked at the Formatter.formatTime, but confused. I appreciate your help to achieve my goal. Thank you.

Solution 1:

From the official documentation regarding the Formatter class:

The constructor takes two optional arguments: a message format string and a date format string.

So change

# create formatter
formatter = logging.Formatter("%(asctime)s;%(levelname)s;%(message)s")

to

# create formatter
formatter = logging.Formatter("%(asctime)s;%(levelname)s;%(message)s",
                              "%Y-%m-%d %H:%M:%S")

Solution 2:

Using logging.basicConfig, the following example works for me:

logging.basicConfig(
    filename='HISTORYlistener.log',
    level=logging.DEBUG,
    format='%(asctime)s.%(msecs)03d %(levelname)s %(module)s - %(funcName)s: %(message)s',
    datefmt='%Y-%m-%d %H:%M:%S',
)

This allows you to format & config all in one line. A resulting log record looks as follows:

2014-05-26 12:22:52.376 CRITICAL historylistener - main: History log failed to start

Solution 3:

To add to the other answers, here are the variable list from Python Documentation.

Directive   Meaning Notes

%a  Locale’s abbreviated weekday name.   
%A  Locale’s full weekday name.  
%b  Locale’s abbreviated month name.     
%B  Locale’s full month name.    
%c  Locale’s appropriate date and time representation.   
%d  Day of the month as a decimal number [01,31].    
%H  Hour (24-hour clock) as a decimal number [00,23].    
%I  Hour (12-hour clock) as a decimal number [01,12].    
%j  Day of the year as a decimal number [001,366].   
%m  Month as a decimal number [01,12].   
%M  Minute as a decimal number [00,59].  
%p  Locale’s equivalent of either AM or PM. (1)
%S  Second as a decimal number [00,61]. (2)
%U  Week number of the year (Sunday as the first day of the week) as a decimal number [00,53]. All days in a new year preceding the first Sunday are considered to be in week 0.    (3)
%w  Weekday as a decimal number [0(Sunday),6].   
%W  Week number of the year (Monday as the first day of the week) as a decimal number [00,53]. All days in a new year preceding the first Monday are considered to be in week 0.    (3)
%x  Locale’s appropriate date representation.    
%X  Locale’s appropriate time representation.    
%y  Year without century as a decimal number [00,99].    
%Y  Year with century as a decimal number.   
%z  Time zone offset indicating a positive or negative time difference from UTC/GMT of the form +HHMM or -HHMM, where H represents decimal hour digits and M represents decimal minute digits [-23:59, +23:59].  
%Z  Time zone name (no characters if no time zone exists).   
%%  A literal '%' character.