Python logging.Formatter(): is there any way to fix the width of a field and justify it left/right?
Question:
Here’s a sample of log records from the logging tutorial:
2005-03-19 15:38:55,977 - simpleExample - DEBUG - debug message
2005-03-19 15:38:55,979 - simpleExample - INFO - info message
2005-03-19 15:38:56,054 - simpleExample - WARNING - warn message
2005-03-19 15:38:56,055 - simpleExample - ERROR - error message
2005-03-19 15:38:56,130 - simpleExample - CRITICAL - critical message
This trailing jaggedness annoys me to no end.
I really want to be able to format like this:
2005-03-19 15:38:55,977 - simpleExample - DEBUG - debug message
2005-03-19 15:38:55,979 - simpleExample - INFO - info message
2005-03-19 15:38:56,054 - simpleExample - WARNING - warn message
2005-03-19 15:38:56,055 - simpleExample - ERROR - error message
2005-03-19 15:38:56,130 - simpleExample - CRITICAL - critical message
I’ve attempted the following for my logger, which doesn’t work (abbreviated code):
fmt = "{0:>8}"
formatter = logging.Formatter("%(asctime)s %(filename)s: " + fmt.format("%(levelname)s") + " %(message)s", "%Y/%m/%d %H:%M:%S")
This executes fine and prints the level name as always, but it doesn’t implement the width format.
Ex.
logger.debug("testing debug message")
logger.info("some random info")
logger.critical("oh crap!")
Actual result:
2013/12/16 13:43:10 logtester: DEBUG testing debug message
2013/12/16 13:43:10 logtester: INFO some random info
2013/12/16 13:43:10 logtester: CRITICAL oh crap!
Desired result:
2013/12/16 13:43:10 logtester: DEBUG testing debug message
2013/12/16 13:43:10 logtester: INFO some random info
2013/12/16 13:43:10 logtester: CRITICAL oh crap!
Any hints to implement a fixed width of a field in a logging.Formatter()?
Using Python 2.6.9.
EDIT: second attempt using another method:
formatter = logging.Formatter("%(asctime)s %(filename)s: " + "%(foo)5s" % {"foo" : "(%(levelname)s)"} + " %(message)s", "%Y/%m/%d %H:%M:%S")
Still results in:
2013/12/16 13:43:10 logtester: DEBUG testing debug message
2013/12/16 13:43:10 logtester: INFO some random info
2013/12/16 13:43:10 logtester: CRITICAL oh crap!
Maybe I’m just doing something boneheaded.
Answers:
Field width can be specified by adding a number in front of the type specifier:
>>> "%(foo)8s" % {'foo': 'bar'}
' bar'
You can use this in your format string passed to the formatter. For your example, that’d be:
"%(asctime)s %(filename)s: %(levelname)8s %(message)s"
Logging (as of 3.2) provides improved support for bracket string format styles. For example, you can now use this kind of formatting:
fomatter = logging.Formatter('{asctime} {name} {levelname:^8s} {message}', style='{')
Which produces center aligned log level. I don’t think this is possibile with % formatted strings.
2021-10-19 14:27:05,799 __main__ DEBUG Debug message
2021-10-19 14:27:05,800 __main__ INFO Info message
2021-10-19 14:27:05,800 __main__ WARNING Warning message
2021-10-19 14:27:05,801 __main__ ERROR Error message
and
'{asctime} {name} {levelname:<8s} {message}'
to align right
2021-10-19 14:26:45,408 __main__ DEBUG Debug message
2021-10-19 14:26:45,409 __main__ INFO Info message
2021-10-19 14:26:45,410 __main__ WARNING Warning message
2021-10-19 14:26:45,410 __main__ ERROR Error message
or
'{asctime} {name} {levelname:>8s} {message}'
to align left
2021-10-19 14:26:25,761 __main__ DEBUG Debug message
2021-10-19 14:26:25,761 __main__ INFO Info message
2021-10-19 14:26:25,762 __main__ WARNING Warning message
2021-10-19 14:26:25,762 __main__ ERROR Error message
Here’s a sample of log records from the logging tutorial:
2005-03-19 15:38:55,977 - simpleExample - DEBUG - debug message
2005-03-19 15:38:55,979 - simpleExample - INFO - info message
2005-03-19 15:38:56,054 - simpleExample - WARNING - warn message
2005-03-19 15:38:56,055 - simpleExample - ERROR - error message
2005-03-19 15:38:56,130 - simpleExample - CRITICAL - critical message
This trailing jaggedness annoys me to no end.
I really want to be able to format like this:
2005-03-19 15:38:55,977 - simpleExample - DEBUG - debug message
2005-03-19 15:38:55,979 - simpleExample - INFO - info message
2005-03-19 15:38:56,054 - simpleExample - WARNING - warn message
2005-03-19 15:38:56,055 - simpleExample - ERROR - error message
2005-03-19 15:38:56,130 - simpleExample - CRITICAL - critical message
I’ve attempted the following for my logger, which doesn’t work (abbreviated code):
fmt = "{0:>8}"
formatter = logging.Formatter("%(asctime)s %(filename)s: " + fmt.format("%(levelname)s") + " %(message)s", "%Y/%m/%d %H:%M:%S")
This executes fine and prints the level name as always, but it doesn’t implement the width format.
Ex.
logger.debug("testing debug message")
logger.info("some random info")
logger.critical("oh crap!")
Actual result:
2013/12/16 13:43:10 logtester: DEBUG testing debug message
2013/12/16 13:43:10 logtester: INFO some random info
2013/12/16 13:43:10 logtester: CRITICAL oh crap!
Desired result:
2013/12/16 13:43:10 logtester: DEBUG testing debug message
2013/12/16 13:43:10 logtester: INFO some random info
2013/12/16 13:43:10 logtester: CRITICAL oh crap!
Any hints to implement a fixed width of a field in a logging.Formatter()?
Using Python 2.6.9.
EDIT: second attempt using another method:
formatter = logging.Formatter("%(asctime)s %(filename)s: " + "%(foo)5s" % {"foo" : "(%(levelname)s)"} + " %(message)s", "%Y/%m/%d %H:%M:%S")
Still results in:
2013/12/16 13:43:10 logtester: DEBUG testing debug message
2013/12/16 13:43:10 logtester: INFO some random info
2013/12/16 13:43:10 logtester: CRITICAL oh crap!
Maybe I’m just doing something boneheaded.
Field width can be specified by adding a number in front of the type specifier:
>>> "%(foo)8s" % {'foo': 'bar'}
' bar'
You can use this in your format string passed to the formatter. For your example, that’d be:
"%(asctime)s %(filename)s: %(levelname)8s %(message)s"
Logging (as of 3.2) provides improved support for bracket string format styles. For example, you can now use this kind of formatting:
fomatter = logging.Formatter('{asctime} {name} {levelname:^8s} {message}', style='{')
Which produces center aligned log level. I don’t think this is possibile with % formatted strings.
2021-10-19 14:27:05,799 __main__ DEBUG Debug message
2021-10-19 14:27:05,800 __main__ INFO Info message
2021-10-19 14:27:05,800 __main__ WARNING Warning message
2021-10-19 14:27:05,801 __main__ ERROR Error message
and
'{asctime} {name} {levelname:<8s} {message}'
to align right
2021-10-19 14:26:45,408 __main__ DEBUG Debug message
2021-10-19 14:26:45,409 __main__ INFO Info message
2021-10-19 14:26:45,410 __main__ WARNING Warning message
2021-10-19 14:26:45,410 __main__ ERROR Error message
or
'{asctime} {name} {levelname:>8s} {message}'
to align left
2021-10-19 14:26:25,761 __main__ DEBUG Debug message
2021-10-19 14:26:25,761 __main__ INFO Info message
2021-10-19 14:26:25,762 __main__ WARNING Warning message
2021-10-19 14:26:25,762 __main__ ERROR Error message