UTF-8 In Python logging, how?

Having code like:

raise Exception(u'щ')

Caused:

  File "/usr/lib/python2.7/logging/__init__.py", line 467, in format
    s = self._fmt % record.__dict__
UnicodeEncodeError: 'ascii' codec can't encode characters in position 0-3: ordinal not in range(128)

This happens because the format string is a byte string, while some of the format string arguments are unicode strings with non-ASCII characters:

>>> "%(message)s" % {'message': Exception(u'\u0449')}
*** UnicodeEncodeError: 'ascii' codec can't encode character u'\u0449' in position 0: ordinal not in range(128)

Making the format string unicode fixes the issue:

>>> u"%(message)s" % {'message': Exception(u'\u0449')}
u'\u0449'

So, in your logging configuration make all format string unicode:

'formatters': {
    'simple': {
        'format': u'%(asctime)-s %(levelname)s [%(name)s]: %(message)s',
        'datefmt': '%Y-%m-%d %H:%M:%S',
    },
 ...

And patch the default logging formatter to use unicode format string:

logging._defaultFormatter = logging.Formatter(u"%(message)s")

Check that you have the latest Python 2.6 - some Unicode bugs were found and fixed since 2.6 came out. For example, on my Ubuntu Jaunty system, I ran your script copied and pasted, removing only the '/home/ted/' prefix from the log file name. Result (copied and pasted from a terminal window):

vinay@eta-jaunty:~/projects/scratch$ python --version
Python 2.6.2
vinay@eta-jaunty:~/projects/scratch$ python utest.py 
printed unicode object: ô
vinay@eta-jaunty:~/projects/scratch$ cat logfile.txt 
ô
vinay@eta-jaunty:~/projects/scratch$ 

On a Windows box:

C:\temp>python --version
Python 2.6.2

C:\temp>python utest.py
printed unicode object: ô

And the contents of the file:

This might also explain why Lennart Regebro couldn't reproduce it either.