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Diffstat (limited to 'Doc/howto/logging-cookbook.rst')
| -rw-r--r-- | Doc/howto/logging-cookbook.rst | 76 |
1 files changed, 19 insertions, 57 deletions
diff --git a/Doc/howto/logging-cookbook.rst b/Doc/howto/logging-cookbook.rst index cdd4b66..acf80b9 100644 --- a/Doc/howto/logging-cookbook.rst +++ b/Doc/howto/logging-cookbook.rst @@ -524,69 +524,31 @@ customized strings with your :class:`Formatter` instances which know about the keys of the dict-like object. If you need a different method, e.g. if you want to prepend or append the contextual information to the message string, you just need to subclass :class:`LoggerAdapter` and override :meth:`process` -to do what you need. Here's an example script which uses this class, which -also illustrates what dict-like behaviour is needed from an arbitrary -'dict-like' object for use in the constructor:: +to do what you need. Here is a simple example:: - import logging + class CustomAdapter(logging.LoggerAdapter): + """ + This example adapter expects the passed in dict-like object to have a + 'connid' key, whose value in brackets is prepended to the log message. + """ + def process(self, msg, kwargs): + return '[%s] %s' % (self.extra['connid'], msg), kwargs - class ConnInfo: - """ - An example class which shows how an arbitrary class can be used as - the 'extra' context information repository passed to a LoggerAdapter. - """ +which you can use like this:: - def __getitem__(self, name): - """ - To allow this instance to look like a dict. - """ - from random import choice - if name == 'ip': - result = choice(['127.0.0.1', '192.168.0.1']) - elif name == 'user': - result = choice(['jim', 'fred', 'sheila']) - else: - result = self.__dict__.get(name, '?') - return result + logger = logging.getLogger(__name__) + adapter = CustomAdapter(logger, {'connid': some_conn_id}) - def __iter__(self): - """ - To allow iteration over keys, which will be merged into - the LogRecord dict before formatting and output. - """ - keys = ['ip', 'user'] - keys.extend(self.__dict__.keys()) - return keys.__iter__() +Then any events that you log to the adapter will have the value of +``some_conn_id`` prepended to the log messages. - if __name__ == '__main__': - from random import choice - levels = (logging.DEBUG, logging.INFO, logging.WARNING, logging.ERROR, logging.CRITICAL) - a1 = logging.LoggerAdapter(logging.getLogger('a.b.c'), - { 'ip' : '123.231.231.123', 'user' : 'sheila' }) - logging.basicConfig(level=logging.DEBUG, - format='%(asctime)-15s %(name)-5s %(levelname)-8s IP: %(ip)-15s User: %(user)-8s %(message)s') - a1.debug('A debug message') - a1.info('An info message with %s', 'some parameters') - a2 = logging.LoggerAdapter(logging.getLogger('d.e.f'), ConnInfo()) - for x in range(10): - lvl = choice(levels) - lvlname = logging.getLevelName(lvl) - a2.log(lvl, 'A message at %s level with %d %s', lvlname, 2, 'parameters') +Using objects other than dicts to pass contextual information +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -When this script is run, the output should look something like this:: - - 2008-01-18 14:49:54,023 a.b.c DEBUG IP: 123.231.231.123 User: sheila A debug message - 2008-01-18 14:49:54,023 a.b.c INFO IP: 123.231.231.123 User: sheila An info message with some parameters - 2008-01-18 14:49:54,023 d.e.f CRITICAL IP: 192.168.0.1 User: jim A message at CRITICAL level with 2 parameters - 2008-01-18 14:49:54,033 d.e.f INFO IP: 192.168.0.1 User: jim A message at INFO level with 2 parameters - 2008-01-18 14:49:54,033 d.e.f WARNING IP: 192.168.0.1 User: sheila A message at WARNING level with 2 parameters - 2008-01-18 14:49:54,033 d.e.f ERROR IP: 127.0.0.1 User: fred A message at ERROR level with 2 parameters - 2008-01-18 14:49:54,033 d.e.f ERROR IP: 127.0.0.1 User: sheila A message at ERROR level with 2 parameters - 2008-01-18 14:49:54,033 d.e.f WARNING IP: 192.168.0.1 User: sheila A message at WARNING level with 2 parameters - 2008-01-18 14:49:54,033 d.e.f WARNING IP: 192.168.0.1 User: jim A message at WARNING level with 2 parameters - 2008-01-18 14:49:54,033 d.e.f INFO IP: 192.168.0.1 User: fred A message at INFO level with 2 parameters - 2008-01-18 14:49:54,033 d.e.f WARNING IP: 192.168.0.1 User: sheila A message at WARNING level with 2 parameters - 2008-01-18 14:49:54,033 d.e.f WARNING IP: 127.0.0.1 User: jim A message at WARNING level with 2 parameters +You don't need to pass an actual dict to a :class:`LoggerAdapter` - you could +pass an instance of a class which implements ``__getitem__`` and ``__iter__`` so +that it looks like a dict to logging. This would be useful if you want to +generate values dynamically (whereas the values in a dict would be constant). .. _filters-contextual: |