Config5

IPython/config/application.py

@@ -0,0 +1,134 @@
+# 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 SingletonConfigurable
+from IPython.utils.traitlets import (
+    Unicode, List, Int, Enum
+)
+from IPython.config.loader import (
+    KeyValueConfigLoader, PyFileConfigLoader
+)
+
+#-----------------------------------------------------------------------------
+# Application class
+#-----------------------------------------------------------------------------
+
+
+class Application(SingletonConfigurable):
+    """A singleton application with full configuration support."""
+
+    # 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')
+
+    # The log level for the application
+    log_level = Enum((0,10,20,30,40,50), default_value=logging.WARN,
+                     config=True, shortname="log_level",
+                     help="Set the log level (0,10,20,30,40,50).")
+
+    def __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):
+        """Fire the traits events when the config is updated."""
+        # 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."""
+        argv = sys.argv[1:] if argv is None else argv
+
+        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)
+

IPython/config/configurable.py

@@ -22,11 +22,10 @@
 
 from copy import deepcopy
 import datetime
-from weakref import WeakValueDictionary
 
-from IPython.utils.importstring import import_item
 from loader import Config
 from IPython.utils.traitlets import HasTraits, Instance
+from IPython.utils.text import indent
 
 
 #-----------------------------------------------------------------------------
@@ -38,6 +37,9 @@ class ConfigurableError(Exception):
     pass
 
 
+class MultipleInstanceError(ConfigurableError):
+    pass
+
 #-----------------------------------------------------------------------------
 # Configurable implementation
 #-----------------------------------------------------------------------------
@@ -137,3 +139,102 @@ def _config_changed(self, name, old, new):
                         # shared by all instances, effectively making it a class attribute.
                         setattr(self, k, deepcopy(config_value))
 
+    @classmethod
+    def class_get_shortnames(cls):
+        """Return the shortname to fullname dict for config=True traits."""
+        cls_traits = cls.class_traits(config=True)
+        shortnames = {}
+        for k, v in cls_traits.items():
+            shortname = v.get_metadata('shortname')
+            if shortname is not None:
+                longname = cls.__name__ + '.' + k
+                shortnames[shortname] = longname
+        return shortnames
+
+    @classmethod
+    def class_get_help(cls):
+        """Get the help string for this class in ReST format."""
+        cls_traits = cls.class_traits(config=True)
+        final_help = []
+        final_help.append(u'%s options' % cls.__name__)
+        final_help.append(len(final_help[0])*u'-')
+        for k, v in cls_traits.items():
+            help = v.get_metadata('help')
+            shortname = v.get_metadata('shortname')
+            header = "%s.%s : %s" % (cls.__name__, k, v.__class__.__name__)
+            if shortname is not None:
+                header += " (shortname=" + shortname + ")"
+            final_help.append(header)
+            if help is not None:
+                final_help.append(indent(help))
+        return '\n'.join(final_help)
+
+    @classmethod
+    def class_print_help(cls):
+        print cls.class_get_help()
+
+
+class SingletonConfigurable(Configurable):
+    """A configurable that only allows one instance.
+
+    This class is for classes that should only have one instance of itself
+    or *any* subclass. To create and retrieve such a class use the
+    :meth:`SingletonConfigurable.instance` method.
+    """
+
+    _instance = None
+
+    @classmethod
+    def instance(cls, *args, **kwargs):
+        """Returns a global instance of this class.
+
+        This method create a new instance if none have previously been created
+        and returns a previously created instance is one already exists.
+
+        The arguments and keyword arguments passed to this method are passed
+        on to the :meth:`__init__` method of the class upon instantiation.
+
+        Examples
+        --------
+
+        Create a singleton class using instance, and retrieve it::
+
+            >>> from IPython.config.configurable import SingletonConfigurable
+            >>> class Foo(SingletonConfigurable): pass
+            >>> foo = Foo.instance()
+            >>> foo == Foo.instance()
+            True
+
+        Create a subclass that is retrived using the base class instance::
+
+            >>> class Bar(SingletonConfigurable): pass
+            >>> class Bam(Bar): pass
+            >>> bam = Bam.instance()
+            >>> bam == Bar.instance()
+            True
+        """
+        # Create and save the instance
+        if cls._instance is None:
+            inst = cls(*args, **kwargs)
+            # Now make sure that the instance will also be returned by
+            # the subclasses instance attribute.
+            for subclass in cls.mro():
+                if issubclass(cls, subclass) and \
+                issubclass(subclass, SingletonConfigurable) and \
+                subclass != SingletonConfigurable:
+                    subclass._instance = inst
+                else:
+                    break
+        if isinstance(cls._instance, cls):
+            return cls._instance
+        else:
+            raise MultipleInstanceError(
+                'Multiple incompatible subclass instances of '
+                '%s are being created.' % cls.__name__
+            )
+
+    @classmethod
+    def initialized(cls):
+        """Has an instance been created?"""
+        return hasattr(cls, "_instance") and cls._instance is not None
+