[issue40053] Document the behavior that no interplotation is applied when no *args are passed in for logging statements

[Nan Hua]

New submission from Nan Hua <nanhua2013 at gmail.com>:

As I see, Python's logging module's implementation has a nice property that, when no additional args are passed in, the msg (first argument) will be directly printed.

For example, logging.error('abc %s') can be handled peacefully with printing "ERROR:root:abc %s" in the log.

However, the logging's documentation only said the followings:
"The msg is the message format string, and the args are the arguments which are merged into msg using the string formatting operator."

>From what I see, this implementation (seems the case for both Python2 and Python3) has many benefits: saving CPU resources, safe handling pre-formated string, etc. More importantly, it also de-facto allows using the convenient f-string in logging statement, e.g. 

logging.error(f'Started at {start_time}, finished at {finish_time}'
              f' by user {user}')

can run correctly and smoothly even with user containing %s inside.

In summary, I hope this de-facto actual behavior can be officially endorsed, with wordings like,
"When *args is empty, i.e. no additional positional arguments passed in, the msg be of any string (no need to be a format string) and will be directly used as is without interpolation."

What do you think? Thank you a lot!

----------
components: Library (Lib)
messages: 364920
nosy: nhua
priority: normal
severity: normal
status: open
title: Document the behavior that no interplotation is applied when no *args are passed in for logging statements
type: behavior
versions: Python 3.9

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue40053>
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