IPython.config.application.Application updates.

* Application now subclasses SingletonConfigurable.
* Added logging support.

IPython/config/application.py

@@ -1,108 +1,130 b''
 # encoding: utf-8
 """
 A base class for a configurable application.
 
 Authors:
 
 * Brian Granger
 """
 
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2008-2011  The IPython Development Team
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 from copy import deepcopy
+import logging
 import sys
 
-from IPython.config.configurable import Configurable
+from IPython.config.configurable import SingletonConfigurable
 from IPython.utils.traitlets import (
-    Unicode, List
+    Unicode, List, Int
 )
 from IPython.config.loader import (
     KeyValueConfigLoader, PyFileConfigLoader
 )
 
 #-----------------------------------------------------------------------------
 # Application class
 #-----------------------------------------------------------------------------
 
 
-class Application(Configurable):
+class Application(SingletonConfigurable):
 
     # The name of the application, will usually match the name of the command
     # line application
     app_name = Unicode(u'application')
 
     # The description of the application that is printed at the beginning
     # of the help.
     description = Unicode(u'This is an application.')
 
     # A sequence of Configurable subclasses whose config=True attributes will
     # be exposed at the command line (shortnames and help).
     classes = List([])
 
     # The version string of this application.
     version = Unicode(u'0.0')
 
+    log_level = Int(logging.WARN, config=True, shortname="log_level")
+
     def __init__(self, **kwargs):
-        Configurable.__init__(self, **kwargs)
+        SingletonConfigurable.__init__(self, **kwargs)
         # Add my class to self.classes so my attributes appear in command line
         # options.
         self.classes.insert(0, self.__class__)
+        self.init_logging()
+
+    def init_logging(self):
+        """Start logging for this application.
+
+        The default is to log to stdout using a StreaHandler. The log level
+        starts at loggin.WARN, but this can be adjusted by setting the 
+        ``log_level`` attribute.
+        """
+        self.log = logging.getLogger(self.__class__.__name__)
+        self.log.setLevel(self.log_level)
+        self._log_handler = logging.StreamHandler()
+        self._log_formatter = logging.Formatter("[%(name)s] %(message)s")
+        self._log_handler.setFormatter(self._log_formatter)
+        self.log.addHandler(self._log_handler)
+
+    def _log_level_changed(self, name, old, new):
+        """Adjust the log level when log_level is set."""
+        self.log.setLevel(new)
 
     def print_help(self):
         """Print the help for each Configurable class in self.classes."""
         for cls in self.classes:
             cls.class_print_help()
             print
 
     def print_description(self):
         """Print the application description."""
         print self.description
         print
 
     def print_version(self):
         """Print the version string."""
         print self.version
 
     def update_config(self, config):
         # Save a copy of the current config.
         newconfig = deepcopy(self.config)
         # Merge the new config into the current one.
         newconfig._merge(config)
         # Save the combined config as self.config, which triggers the traits
         # events.
         self.config = config
 
     def parse_command_line(self, argv=None):
         """Parse the command line arguments."""
         if argv is None:
             argv = sys.argv[1:]
 
         if '-h' in argv or '--h' in argv:
             self.print_description()
             self.print_help()
             sys.exit(1)
 
         if '--version' in argv:
             self.print_version()
             sys.exit(1)
 
         loader = KeyValueConfigLoader(argv=argv, classes=self.classes)
         config = loader.load_config()
         self.update_config(config)
 
     def load_config_file(self, filename, path=None):
         """Load a .py based config file by filename and path."""
         # TODO: this raises IOError if filename does not exist.
         loader = PyFileConfigLoader(filename, path=path)
         config = loader.load_config()
         self.update_config(config)