ANN: Logging Package v0.4.9.2 released

Vinay Sajip
28 Feb 2004 15:43:41 -0800

A new version of the Python logging package has been released. If you
are using version 2.3 of later of Python, this release will not mean
much to you - it is the same as recent checkins into Python CVS.
However, this release fixes numerous bugs reported since the last
independent release (0.4.7), and may be of interest to people using
earlier versions of Python.

What Does It Do?
The logging package offers the ability for any Python program to log
events which occur during program execution. It's typically used to
provide application diagnostics, warnings and error messages. In
addition to capturing "what happened", "where it happened", "when it
happened", "how important it is" and event specific data, you can
configure, without changing the application source code, both the
verbosity of logging and the routing of events to different
destinations such as console, disk files, sockets, email addresses,
Web servers, SOAP servers etc. etc. You can even change the
configuration of a running program without stopping and restarting it!

You can use the logging package in exception handlers, and it will
include traceback information in the log. It's thread-safe, and very
easy to use - just "import logging" and log away! Classes provided

Logger	- used to log messages for a particular area of an application.
You can instantiate these wherever you want, there's no need to pass
references to them around your application. You can log events based
on importance levels of DEBUG (least important), INFO, WARN, ERROR,
and CRITICAL (most important). You can define your own levels if the
default levels don't meet your requirements.

Handler - used to route events to particular destinations. Handlers
included are:
   StreamHandler (for generalized streams, including console)
   FileHandler (for disk files - including log file rotation with size
limits for log files)
   SocketHandler (for sending events to a TCP socket)
   DatagramHandler (for sending events to a UDP socket - faster, but
less reliable than TCP)
   SMTPHandler (send events to arbitrary email addresses)
   HTTPHandler (send events to Web servers)
   SysLogHandler (send events to Unix syslog)
   MemoryHandler (batch up events and process them several at a time)
   NTEventLogHandler (send events to Windows NT event logs)
There are also examples of XMLHandler and SOAPHandler in the

Formatter - used to format events as text strings. Flexible "msg %
arg_tuple" formatting is the basis for formatting, with flexible
date/time formatting including ISO8601 and any strftime-based formats.

Filter - used when filtering based on importance
distribution includes examples of filters based on class matching,
regular expression matching, value matching, and logger matching.

In the unlikely event that you're daunted by all the apparent
complexity, fear not. The package offers a simple function-based
interface to allow very simple, almost casual use of the underlying

In addition to the core logging functionality, you get the ability to
configure logging using a ConfigParser-based text file format, a
Tkinter-based GUI configurator which creates configuration files for
you, and a simple network-based event receiver which receives events
on TCP, UDP, HTTP and SOAP ports. This is suitable for testing and
might perhaps serve as a model for your own event receivers. Also
included are over 20 test scripts which serve both as test harnesses
and examples of how to use the logging package.

You can get more information from

There are "download" and "recent changes" links at the top of that
page. API documentation is available at

As always, your feedback is most welcome (especially bug reports,
patches and suggestions for improvement). Enjoy!


Vinay Sajip
Red Dove Consultants Ltd.

Changes since the last independent release:
Traceback text is now cached.
Tracebacks can be propagated across sockets as text.
Added makeLogRecord() to allow a LogRecord to be
created from a dictionary.
Closing a handler now removes it from the internal list
used by shutdown().
Made close() call flush() for handlers where this makes
sense (thanks to Jim Jewett).
The exc_info keyword parameter can be used to pass an
exception tuple as well as a flag indicating that the
current exception should be logged.
A shutdown hook is registered to call shutdown() on
application (Python) exit (thanks to Jim Jewett).
Removed redundant error check in setLoggerClass().
Added RESET_ERROR to logging.config.
SocketHandler now uses an exponential backoff strategy
(thanks to Robert Olson).
Made _listener global in stopListening().
Made listen() correctly pass the specified port.
Removed some redundant imports in
Added the record being processed as a parameter to
handleError (thanks to Gordon den Otter for the idea).
Handler.handle returns the result of applying the
filter to the record (thanks to Gordon den Otter for
the idea).
Added a seek(0, 2) in RotatingFileHandler before the
tell() call. This is because under Windows, tell()
returns 0 until the first actual write (thanks to
Gordon den Otter for the patch).
Altered findCaller to not use inspect (thanks to
Jeremy Hylton for the patch).
Renamed warn and WARN to warning and WARNING. This may
break existing code, but the standard Python module
will use warning/WARNING rather than warn/WARN. The
fatal and FATAL synonyms for critical and CRITICAL
have also been removed.
Added defaultEncoding and some support for encoding
Unicode messages (thanks to Stéphane Bidoul for the
Added process ID to the list of LogRecord attributes.
Modified Logger.removeHandler so that it does not
close the handler on removal.
Modified SMTPHandler to treat a single "to address"
correctly (thanks to Anthony Baxter).
Modified SMTPHandler to add a date header to the SMTP
message (thanks to David Driver for the suggestion).
Modified HTTPHandler to factor out the mapping of
a LogRecord to a dictionary (thanks to Franz Glasner
for the patch).
Minor documentation corrections.