[ python-Feature Requests-1190689 ] logging module '.' behavior

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Feature Requests item #1190689, was opened at 2005-04-26 20:19
Message generated for change (Comment added) made by cxdunn
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Category: Python Library
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Christopher Dunn (cxdunn)
Assigned to: Vinay Sajip (vsajip)
Summary: logging module '.' behavior

Initial Comment:
I would like a trailing '.' to be ignored in names
passed to getLogger(), like a trainling '/' in a Unix path.

In module 'foo':
logfoo = getLogger('.foo.')
# logger '"" should be the parent of ".foo"

Elsewhere, controlled by the user of that module:
import foo
logdefault = getLogger('.')
hdlr = StreamHandler()
fmtr = Formatter("%(name)s:%(msg)s")
hdlr.setFormatter(fmtr)
logdefault.addHandler(hdlr)


Given this change, I would also like the name of the
default logger to be displayed as '.', or even "",
rather than 'root'. The current behavior is odd:

logfoo.info("Foo message")
displays
.foo:Foo message
buf
logdefault.info("Default message")
displays
root:Default message

I NEVER mentioned the word "root" anywhere! And I don't
think it's very descriptive.

I would rather see ANY of these:
:Default message
.:Default message
default:Default message
logging:Default message

These changes would make the system more intuitive.

-cxdunn

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>Comment By: Christopher Dunn (cxdunn)
Date: 2005-04-28 02:21

Message:
Logged In: YES 
user_id=1267419

I am attaching a first pass it it.

I've stored the "absolute" names everywhere, including both
leading and trailing '.'

I call this "absolute" by analogy with os.path.abspath(). I
believe that similarities within the Python library help the
user remember key concepts.

What's missing:

 * I don't have aliases.
 * The "current working logger" is always '.'
 * And I haven't added any extra tags for the Formatter.

But those are all very simple changes. The tough part is
getting the path-searching correct. I have a big UnitTest
suite which I can send to you if you'd like.

The most important thing is that the word "root" is
completely gone, but perhaps %(name)s should translate '.'
to 'root' for backwards compatibility.

The second-most important thing is that getLogger('.')
returns the root logger.

Third is that getLogger("Package.Module") is equivalent to
getLogger(".Package.Module.")

As for tags in the Formatter, after some testing I suggest
these:

%(name)s => abspath.rstrip('.'), but "." becomes "root"
%(absname)s => abspath, with leading AND trailing dot, like
a directory, so there is no question about whether the root
displays as "." or "". It is always just dot in absolute
notation.
%(logger)s => abspath.rstrip('.'), maybe the prettiest

I must tell you that, once I figured out how the logging
module works, I really love it!

Other possible additions:

* Some useful, predefined filter classes: Never, OneTime
(which must have a reset() method to clear its cache). I can
send my version if you want.
* A PipedStreamHandler. I'm not sure how to make this work.
The idea is that, in UnitTesting, I want to read from some
stream immediately after an operation, and I want the logged
data to be immediately available, but to disappear as soon
as I've read it. Does that make sense? Right now, I use a
cStringIO object, with s.seek(0); s.truncate() after every read.

-cxdunn

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Comment By: Christopher Dunn (cxdunn)
Date: 2005-04-27 15:37

Message:
Logged In: YES 
user_id=1267419

Novices always ask, "Why did it print 'root'? Where did that
come from? 
After discussing this with some other "logging" module
users, I think we've come up with a very good idea, which
would maintain BACKWARDS COMPATIBILITY.

Essentially, treat the logging module as a shell and the
logger name as a path. Specifically,

* Let the global logging functions operate on the "current
worrking logger", which by default is "." (Let "root" be an
alias for ".")
* Change getLogger() so that it works on both absolute and
relative logger paths. (Since the default current logger is
"root", we maintain backwards compatibility.)
* Change the format function so that %(name)s shows the
relative path, if the absolute path starts with the current
working logger name.
* Add a format keyword, %(absname)s, which prints the
absolute logger path.
* Add another format keyword, %(logger)s, which prints what
most people expect to see: the absolute logger name, sans
the leading dot. (The "root" or "." logger would display as
"", exactly the way it is usually accessed.)
* Add global functions, change_current_logger() and
get_current_logger().
* Add global function, alias(). Always create an alias for
"root" to "."

Examples::
  from logging import *
  log = getLogger() #or getLogger(".") or getLogger("root")
  h1 = StreamHandler()
  f1 = Formatter("[%(name)s]%(message)s")
  h1.setFormatter(f1)
  log.addHandler(h1)
  h2 = StreamHandler()
  f2 = Formatter("[%(absname)s]%(message)s")
  h2.setFormatter(f2)
  log.addHandler(h2)
  h3 = StreamHandler()
  f3 = Formatter("[%(logger)s]%(message)s")
  h3.setFormatter(f3)
  log.addHandler(h3)
  log.error("First message")

  # ...
  child = getLogger("child") # or getLogger(".child")
  child.error("Bad news")

This should print:

[root]First message
[.]First message
[]First message
[child]Bad news
[.child]Bad news
[child]Bad news


This would create tremendous flexibility, add some clarity
to the meaning of the "root" logger, and still maintain
complete backwards compatibility.

I am willing to make the changes myself, including
UnitTests, if there is agreement that they would be adopted.
(Note that String.before() and String.after() would make the
coding a little easier/clearer, but that's a different
feature request.)

-cxdunn

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