Merge pull request #5379 from minrk/config-grr

don't instantiate Application just for default logger

IPython/config/configurable.py

@@ -1,386 +1,390 b''
 # encoding: utf-8
 """
 A base class for objects that are configurable.
 
 Inheritance diagram:
 
 .. inheritance-diagram:: IPython.config.configurable
    :parts: 3
 
 Authors:
 
 * Brian Granger
 * Fernando Perez
 * Min RK
 """
 from __future__ import print_function
 
 #-----------------------------------------------------------------------------
 #  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
 #-----------------------------------------------------------------------------
 
+import logging
 from copy import deepcopy
 
 from .loader import Config, LazyConfigValue
 from IPython.utils.traitlets import HasTraits, Instance
 from IPython.utils.text import indent, wrap_paragraphs
 from IPython.utils.py3compat import iteritems
 
 
 #-----------------------------------------------------------------------------
 # Helper classes for Configurables
 #-----------------------------------------------------------------------------
 
 
 class ConfigurableError(Exception):
     pass
 
 
 class MultipleInstanceError(ConfigurableError):
     pass
 
 #-----------------------------------------------------------------------------
 # Configurable implementation
 #-----------------------------------------------------------------------------
 
 class Configurable(HasTraits):
 
     config = Instance(Config, (), {})
     parent = Instance('IPython.config.configurable.Configurable')
 
     def __init__(self, **kwargs):
         """Create a configurable given a config config.
 
         Parameters
         ----------
         config : Config
             If this is empty, default values are used. If config is a
             :class:`Config` instance, it will be used to configure the
             instance.
         parent : Configurable instance, optional
             The parent Configurable instance of this object.
 
         Notes
         -----
         Subclasses of Configurable must call the :meth:`__init__` method of
         :class:`Configurable` *before* doing anything else and using
         :func:`super`::
 
             class MyConfigurable(Configurable):
                 def __init__(self, config=None):
                     super(MyConfigurable, self).__init__(config=config)
                     # Then any other code you need to finish initialization.
 
         This ensures that instances will be configured properly.
         """
         parent = kwargs.pop('parent', None)
         if parent is not None:
             # config is implied from parent
             if kwargs.get('config', None) is None:
                 kwargs['config'] = parent.config
             self.parent = parent
         
         config = kwargs.pop('config', None)
         if config is not None:
             # We used to deepcopy, but for now we are trying to just save
             # by reference.  This *could* have side effects as all components
             # will share config. In fact, I did find such a side effect in
             # _config_changed below. If a config attribute value was a mutable type
             # all instances of a component were getting the same copy, effectively
             # making that a class attribute.
             # self.config = deepcopy(config)
             self.config = config
         # This should go second so individual keyword arguments override
         # the values in config.
         super(Configurable, self).__init__(**kwargs)
 
     #-------------------------------------------------------------------------
     # Static trait notifiations
     #-------------------------------------------------------------------------
     
     @classmethod
     def section_names(cls):
         """return section names as a list"""
         return  [c.__name__ for c in reversed(cls.__mro__) if
             issubclass(c, Configurable) and issubclass(cls, c)
         ]
     
     def _find_my_config(self, cfg):
         """extract my config from a global Config object
         
         will construct a Config object of only the config values that apply to me
         based on my mro(), as well as those of my parent(s) if they exist.
         
         If I am Bar and my parent is Foo, and their parent is Tim,
         this will return merge following config sections, in this order::
         
             [Bar, Foo.bar, Tim.Foo.Bar]
         
         With the last item being the highest priority.
         """
         cfgs = [cfg]
         if self.parent:
             cfgs.append(self.parent._find_my_config(cfg))
         my_config = Config()
         for c in cfgs:
             for sname in self.section_names():
                 # Don't do a blind getattr as that would cause the config to
                 # dynamically create the section with name Class.__name__.
                 if c._has_section(sname):
                     my_config.merge(c[sname])
         return my_config
     
     def _load_config(self, cfg, section_names=None, traits=None):
         """load traits from a Config object"""
         
         if traits is None:
             traits = self.traits(config=True)
         if section_names is None:
             section_names = self.section_names()
         
         my_config = self._find_my_config(cfg)
         for name, config_value in iteritems(my_config):
             if name in traits:
                 if isinstance(config_value, LazyConfigValue):
                     # ConfigValue is a wrapper for using append / update on containers
                     # without having to copy the 
                     initial = getattr(self, name)
                     config_value = config_value.get_value(initial)
                 # We have to do a deepcopy here if we don't deepcopy the entire
                 # config object. If we don't, a mutable config_value will be
                 # shared by all instances, effectively making it a class attribute.
                 setattr(self, name, deepcopy(config_value))
 
     def _config_changed(self, name, old, new):
         """Update all the class traits having ``config=True`` as metadata.
 
         For any class trait with a ``config`` metadata attribute that is
         ``True``, we update the trait with the value of the corresponding
         config entry.
         """
         # Get all traits with a config metadata entry that is True
         traits = self.traits(config=True)
 
         # We auto-load config section for this class as well as any parent
         # classes that are Configurable subclasses.  This starts with Configurable
         # and works down the mro loading the config for each section.
         section_names = self.section_names()
         self._load_config(new, traits=traits, section_names=section_names)
 
     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 = newconfig
 
     @classmethod
     def class_get_help(cls, inst=None):
         """Get the help string for this class in ReST format.
         
         If `inst` is given, it's current trait values will be used in place of
         class defaults.
         """
         assert inst is None or isinstance(inst, cls)
         final_help = []
         final_help.append(u'%s options' % cls.__name__)
         final_help.append(len(final_help[0])*u'-')
         for k, v in sorted(cls.class_traits(config=True).items()):
             help = cls.class_get_trait_help(v, inst)
             final_help.append(help)
         return '\n'.join(final_help)
 
     @classmethod
     def class_get_trait_help(cls, trait, inst=None):
         """Get the help string for a single trait.
         
         If `inst` is given, it's current trait values will be used in place of
         the class default.
         """
         assert inst is None or isinstance(inst, cls)
         lines = []
         header = "--%s.%s=<%s>" % (cls.__name__, trait.name, trait.__class__.__name__)
         lines.append(header)
         if inst is not None:
             lines.append(indent('Current: %r' % getattr(inst, trait.name), 4))
         else:
             try:
                 dvr = repr(trait.get_default_value())
             except Exception:
                 dvr = None # ignore defaults we can't construct
             if dvr is not None:
                 if len(dvr) > 64:
                     dvr = dvr[:61]+'...'
                 lines.append(indent('Default: %s' % dvr, 4))
         if 'Enum' in trait.__class__.__name__:
             # include Enum choices
             lines.append(indent('Choices: %r' % (trait.values,)))
 
         help = trait.get_metadata('help')
         if help is not None:
             help = '\n'.join(wrap_paragraphs(help, 76))
             lines.append(indent(help, 4))
         return '\n'.join(lines)
 
     @classmethod
     def class_print_help(cls, inst=None):
         """Get the help string for a single trait and print it."""
         print(cls.class_get_help(inst))
 
     @classmethod
     def class_config_section(cls):
         """Get the config class config section"""
         def c(s):
             """return a commented, wrapped block."""
             s = '\n\n'.join(wrap_paragraphs(s, 78))
 
             return '# ' + s.replace('\n', '\n# ')
 
         # section header
         breaker = '#' + '-'*78
         s = "# %s configuration" % cls.__name__
         lines = [breaker, s, breaker, '']
         # get the description trait
         desc = cls.class_traits().get('description')
         if desc:
             desc = desc.default_value
         else:
             # no description trait, use __doc__
             desc = getattr(cls, '__doc__', '')
         if desc:
             lines.append(c(desc))
             lines.append('')
 
         parents = []
         for parent in cls.mro():
             # only include parents that are not base classes
             # and are not the class itself
             # and have some configurable traits to inherit
             if parent is not cls and issubclass(parent, Configurable) and \
                     parent.class_traits(config=True):
                 parents.append(parent)
 
         if parents:
             pstr = ', '.join([ p.__name__ for p in parents ])
             lines.append(c('%s will inherit config from: %s'%(cls.__name__, pstr)))
             lines.append('')
 
         for name, trait in iteritems(cls.class_traits(config=True)):
             help = trait.get_metadata('help') or ''
             lines.append(c(help))
             lines.append('# c.%s.%s = %r'%(cls.__name__, name, trait.get_default_value()))
             lines.append('')
         return '\n'.join(lines)
 
 
 
 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 _walk_mro(cls):
         """Walk the cls.mro() for parent classes that are also singletons
 
         For use in instance()
         """
 
         for subclass in cls.mro():
             if issubclass(cls, subclass) and \
                     issubclass(subclass, SingletonConfigurable) and \
                     subclass != SingletonConfigurable:
                 yield subclass
 
     @classmethod
     def clear_instance(cls):
         """unset _instance for this class and singleton parents.
         """
         if not cls.initialized():
             return
         for subclass in cls._walk_mro():
             if isinstance(subclass._instance, cls):
                 # only clear instances that are instances
                 # of the calling class
                 subclass._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
             # parent classes' _instance attribute.
             for subclass in cls._walk_mro():
                 subclass._instance = inst
 
         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
 
 
 class LoggingConfigurable(Configurable):
     """A parent class for Configurables that log.
 
     Subclasses have a log trait, and the default behavior
     is to get the logger from the currently running Application
     via Application.instance().log.
     """
 
     log = Instance('logging.Logger')
     def _log_default(self):
         from IPython.config.application import Application
-        return Application.instance().log
+        if Application.initialized():
+            return Application.instance().log
+        else:
+            return logging.getLogger()
 
 

IPython/config/loader.py

@@ -1,842 +1,846 b''
 """A simple configuration system.
 
 Inheritance diagram:
 
 .. inheritance-diagram:: IPython.config.loader
    :parts: 3
 
 Authors
 -------
 * Brian Granger
 * Fernando Perez
 * Min RK
 """
 
 #-----------------------------------------------------------------------------
 #  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
 #-----------------------------------------------------------------------------
 
 import argparse
 import copy
+import logging
 import os
 import re
 import sys
 import json
 
 from IPython.utils.path import filefind, get_ipython_dir
 from IPython.utils import py3compat
 from IPython.utils.encoding import DEFAULT_ENCODING
 from IPython.utils.py3compat import unicode_type, iteritems
 from IPython.utils.traitlets import HasTraits, List, Any, TraitError
 
 #-----------------------------------------------------------------------------
 # Exceptions
 #-----------------------------------------------------------------------------
 
 
 class ConfigError(Exception):
     pass
 
 class ConfigLoaderError(ConfigError):
     pass
 
 class ConfigFileNotFound(ConfigError):
     pass
 
 class ArgumentError(ConfigLoaderError):
     pass
 
 #-----------------------------------------------------------------------------
 # Argparse fix
 #-----------------------------------------------------------------------------
 
 # Unfortunately argparse by default prints help messages to stderr instead of
 # stdout.  This makes it annoying to capture long help screens at the command
 # line, since one must know how to pipe stderr, which many users don't know how
 # to do.  So we override the print_help method with one that defaults to
 # stdout and use our class instead.
 
 class ArgumentParser(argparse.ArgumentParser):
     """Simple argparse subclass that prints help to stdout by default."""
 
     def print_help(self, file=None):
         if file is None:
             file = sys.stdout
         return super(ArgumentParser, self).print_help(file)
 
     print_help.__doc__ = argparse.ArgumentParser.print_help.__doc__
 
 #-----------------------------------------------------------------------------
 # Config class for holding config information
 #-----------------------------------------------------------------------------
 
 class LazyConfigValue(HasTraits):
     """Proxy object for exposing methods on configurable containers
     
     Exposes:
     
     - append, extend, insert on lists
     - update on dicts
     - update, add on sets
     """
     
     _value = None
     
     # list methods
     _extend = List()
     _prepend = List()
     
     def append(self, obj):
         self._extend.append(obj)
     
     def extend(self, other):
         self._extend.extend(other)
     
     def prepend(self, other):
         """like list.extend, but for the front"""
         self._prepend[:0] = other
     
     _inserts = List()
     def insert(self, index, other):
         if not isinstance(index, int):
             raise TypeError("An integer is required")
         self._inserts.append((index, other))
     
     # dict methods
     # update is used for both dict and set
     _update = Any()
     def update(self, other):
         if self._update is None:
             if isinstance(other, dict):
                 self._update = {}
             else:
                 self._update = set()
         self._update.update(other)
     
     # set methods
     def add(self, obj):
         self.update({obj})
     
     def get_value(self, initial):
         """construct the value from the initial one
         
         after applying any insert / extend / update changes
         """
         if self._value is not None:
             return self._value
         value = copy.deepcopy(initial)
         if isinstance(value, list):
             for idx, obj in self._inserts:
                 value.insert(idx, obj)
             value[:0] = self._prepend
             value.extend(self._extend)
         
         elif isinstance(value, dict):
             if self._update:
                 value.update(self._update)
         elif isinstance(value, set):
             if self._update:
                 value.update(self._update)
         self._value = value
         return value
     
     def to_dict(self):
         """return JSONable dict form of my data
         
         Currently update as dict or set, extend, prepend as lists, and inserts as list of tuples.
         """
         d = {}
         if self._update:
             d['update'] = self._update
         if self._extend:
             d['extend'] = self._extend
         if self._prepend:
             d['prepend'] = self._prepend
         elif self._inserts:
             d['inserts'] = self._inserts
         return d
 
 
 def _is_section_key(key):
     """Is a Config key a section name (does it start with a capital)?"""
     if key and key[0].upper()==key[0] and not key.startswith('_'):
         return True
     else:
         return False
 
 
 class Config(dict):
     """An attribute based dict that can do smart merges."""
 
     def __init__(self, *args, **kwds):
         dict.__init__(self, *args, **kwds)
         self._ensure_subconfig()
     
     def _ensure_subconfig(self):
         """ensure that sub-dicts that should be Config objects are
         
         casts dicts that are under section keys to Config objects,
         which is necessary for constructing Config objects from dict literals.
         """
         for key in self:
             obj = self[key]
             if _is_section_key(key) \
                     and isinstance(obj, dict) \
                     and not isinstance(obj, Config):
                 setattr(self, key, Config(obj))
     
     def _merge(self, other):
         """deprecated alias, use Config.merge()"""
         self.merge(other)
     
     def merge(self, other):
         """merge another config object into this one"""
         to_update = {}
         for k, v in iteritems(other):
             if k not in self:
                 to_update[k] = copy.deepcopy(v)
             else: # I have this key
                 if isinstance(v, Config) and isinstance(self[k], Config):
                     # Recursively merge common sub Configs
                     self[k].merge(v)
                 else:
                     # Plain updates for non-Configs
                     to_update[k] = copy.deepcopy(v)
 
         self.update(to_update)
 
     def __contains__(self, key):
         # allow nested contains of the form `"Section.key" in config`
         if '.' in key:
             first, remainder = key.split('.', 1)
             if first not in self:
                 return False
             return remainder in self[first]
         
         return super(Config, self).__contains__(key)
     
     # .has_key is deprecated for dictionaries.
     has_key = __contains__
     
     def _has_section(self, key):
         return _is_section_key(key) and key in self
     
     def copy(self):
         return type(self)(dict.copy(self))
 
     def __copy__(self):
         return self.copy()
 
     def __deepcopy__(self, memo):
         import copy
         return type(self)(copy.deepcopy(list(self.items())))
     
     def __getitem__(self, key):
         try:
             return dict.__getitem__(self, key)
         except KeyError:
             if _is_section_key(key):
                 c = Config()
                 dict.__setitem__(self, key, c)
                 return c
             elif not key.startswith('_'):
                 # undefined, create lazy value, used for container methods
                 v = LazyConfigValue()
                 dict.__setitem__(self, key, v)
                 return v
             else:
                 raise KeyError
 
     def __setitem__(self, key, value):
         if _is_section_key(key):
             if not isinstance(value, Config):
                 raise ValueError('values whose keys begin with an uppercase '
                                  'char must be Config instances: %r, %r' % (key, value))
         dict.__setitem__(self, key, value)
 
     def __getattr__(self, key):
         if key.startswith('__'):
             return dict.__getattr__(self, key)
         try:
             return self.__getitem__(key)
         except KeyError as e:
             raise AttributeError(e)
 
     def __setattr__(self, key, value):
         if key.startswith('__'):
             return dict.__setattr__(self, key, value)
         try:
             self.__setitem__(key, value)
         except KeyError as e:
             raise AttributeError(e)
 
     def __delattr__(self, key):
         if key.startswith('__'):
             return dict.__delattr__(self, key)
         try:
             dict.__delitem__(self, key)
         except KeyError as e:
             raise AttributeError(e)
 
 
 #-----------------------------------------------------------------------------
 # Config loading classes
 #-----------------------------------------------------------------------------
 
 
 class ConfigLoader(object):
     """A object for loading configurations from just about anywhere.
 
     The resulting configuration is packaged as a :class:`Config`.
 
     Notes
     -----
     A :class:`ConfigLoader` does one thing: load a config from a source
     (file, command line arguments) and returns the data as a :class:`Config` object.
     There are lots of things that :class:`ConfigLoader` does not do.  It does
     not implement complex logic for finding config files.  It does not handle
     default values or merge multiple configs.  These things need to be
     handled elsewhere.
     """
 
     def _log_default(self):
         from IPython.config.application import Application
-        return Application.instance().log
+        if Application.initialized():
+            return Application.instance().log
+        else:
+            return logging.getLogger()
 
     def __init__(self, log=None):
         """A base class for config loaders.
 
         log : instance of :class:`logging.Logger` to use.
               By default loger of :meth:`IPython.config.application.Application.instance()`
               will be used
 
         Examples
         --------
 
         >>> cl = ConfigLoader()
         >>> config = cl.load_config()
         >>> config
         {}
         """
         self.clear()
         if log is None:
             self.log = self._log_default()
             self.log.debug('Using default logger')
         else:
             self.log = log
 
     def clear(self):
         self.config = Config()
 
     def load_config(self):
         """Load a config from somewhere, return a :class:`Config` instance.
 
         Usually, this will cause self.config to be set and then returned.
         However, in most cases, :meth:`ConfigLoader.clear` should be called
         to erase any previous state.
         """
         self.clear()
         return self.config
 
 
 class FileConfigLoader(ConfigLoader):
     """A base class for file based configurations.
 
     As we add more file based config loaders, the common logic should go
     here.
     """
 
     def __init__(self, filename, path=None, **kw):
         """Build a config loader for a filename and path.
 
         Parameters
         ----------
         filename : str
             The file name of the config file.
         path : str, list, tuple
             The path to search for the config file on, or a sequence of
             paths to try in order.
         """
         super(FileConfigLoader, self).__init__(**kw)
         self.filename = filename
         self.path = path
         self.full_filename = ''
 
     def _find_file(self):
         """Try to find the file by searching the paths."""
         self.full_filename = filefind(self.filename, self.path)
 
 class JSONFileConfigLoader(FileConfigLoader):
     """A Json file loader for config"""
 
     def load_config(self):
         """Load the config from a file and return it as a Config object."""
         self.clear()
         try:
             self._find_file()
         except IOError as e:
             raise ConfigFileNotFound(str(e))
         dct = self._read_file_as_dict()
         self.config = self._convert_to_config(dct)
         return self.config
 
     def _read_file_as_dict(self):
         with open(self.full_filename) as f:
             return json.load(f)
 
     def _convert_to_config(self, dictionary):
         if 'version' in dictionary:
             version = dictionary.pop('version')
         else:
             version = 1
             self.log.warn("Unrecognized JSON config file version, assuming version {}".format(version))
 
         if version == 1:
             return Config(dictionary)
         else:
             raise ValueError('Unknown version of JSON config file: {version}'.format(version=version))
 
 
 class PyFileConfigLoader(FileConfigLoader):
     """A config loader for pure python files.
 
     This is responsible for locating a Python config file by filename and
     path, then executing it to construct a Config object.
     """
 
     def load_config(self):
         """Load the config from a file and return it as a Config object."""
         self.clear()
         try:
             self._find_file()
         except IOError as e:
             raise ConfigFileNotFound(str(e))
         self._read_file_as_dict()
         return self.config
 
 
     def _read_file_as_dict(self):
         """Load the config file into self.config, with recursive loading."""
         # This closure is made available in the namespace that is used
         # to exec the config file.  It allows users to call
         # load_subconfig('myconfig.py') to load config files recursively.
         # It needs to be a closure because it has references to self.path
         # and self.config.  The sub-config is loaded with the same path
         # as the parent, but it uses an empty config which is then merged
         # with the parents.
 
         # If a profile is specified, the config file will be loaded
         # from that profile
 
         def load_subconfig(fname, profile=None):
             # import here to prevent circular imports
             from IPython.core.profiledir import ProfileDir, ProfileDirError
             if profile is not None:
                 try:
                     profile_dir = ProfileDir.find_profile_dir_by_name(
                             get_ipython_dir(),
                             profile,
                     )
                 except ProfileDirError:
                     return
                 path = profile_dir.location
             else:
                 path = self.path
             loader = PyFileConfigLoader(fname, path)
             try:
                 sub_config = loader.load_config()
             except ConfigFileNotFound:
                 # Pass silently if the sub config is not there. This happens
                 # when a user s using a profile, but not the default config.
                 pass
             else:
                 self.config.merge(sub_config)
 
         # Again, this needs to be a closure and should be used in config
         # files to get the config being loaded.
         def get_config():
             return self.config
 
         namespace = dict(
             load_subconfig=load_subconfig,
             get_config=get_config,
             __file__=self.full_filename,
         )
         fs_encoding = sys.getfilesystemencoding() or 'ascii'
         conf_filename = self.full_filename.encode(fs_encoding)
         py3compat.execfile(conf_filename, namespace)
 
 
 class CommandLineConfigLoader(ConfigLoader):
     """A config loader for command line arguments.
 
     As we add more command line based loaders, the common logic should go
     here.
     """
 
     def _exec_config_str(self, lhs, rhs):
         """execute self.config.<lhs> = <rhs>
         
         * expands ~ with expanduser
         * tries to assign with raw eval, otherwise assigns with just the string,
           allowing `--C.a=foobar` and `--C.a="foobar"` to be equivalent.  *Not*
           equivalent are `--C.a=4` and `--C.a='4'`.
         """
         rhs = os.path.expanduser(rhs)
         try:
             # Try to see if regular Python syntax will work. This
             # won't handle strings as the quote marks are removed
             # by the system shell.
             value = eval(rhs)
         except (NameError, SyntaxError):
             # This case happens if the rhs is a string.
             value = rhs
 
         exec(u'self.config.%s = value' % lhs)
 
     def _load_flag(self, cfg):
         """update self.config from a flag, which can be a dict or Config"""
         if isinstance(cfg, (dict, Config)):
             # don't clobber whole config sections, update
             # each section from config:
             for sec,c in iteritems(cfg):
                 self.config[sec].update(c)
         else:
             raise TypeError("Invalid flag: %r" % cfg)
 
 # raw --identifier=value pattern
 # but *also* accept '-' as wordsep, for aliases
 # accepts:  --foo=a
 #           --Class.trait=value
 #           --alias-name=value
 # rejects:  -foo=value
 #           --foo
 #           --Class.trait
 kv_pattern = re.compile(r'\-\-[A-Za-z][\w\-]*(\.[\w\-]+)*\=.*')
 
 # just flags, no assignments, with two *or one* leading '-'
 # accepts:  --foo
 #           -foo-bar-again
 # rejects:  --anything=anything
 #           --two.word
 
 flag_pattern = re.compile(r'\-\-?\w+[\-\w]*$')
 
 class KeyValueConfigLoader(CommandLineConfigLoader):
     """A config loader that loads key value pairs from the command line.
 
     This allows command line options to be gives in the following form::
 
         ipython --profile="foo" --InteractiveShell.autocall=False
     """
 
     def __init__(self, argv=None, aliases=None, flags=None, **kw):
         """Create a key value pair config loader.
 
         Parameters
         ----------
         argv : list
             A list that has the form of sys.argv[1:] which has unicode
             elements of the form u"key=value". If this is None (default),
             then sys.argv[1:] will be used.
         aliases : dict
             A dict of aliases for configurable traits.
             Keys are the short aliases, Values are the resolved trait.
             Of the form: `{'alias' : 'Configurable.trait'}`
         flags : dict
             A dict of flags, keyed by str name. Vaues can be Config objects,
             dicts, or "key=value" strings.  If Config or dict, when the flag
             is triggered, The flag is loaded as `self.config.update(m)`.
 
         Returns
         -------
         config : Config
             The resulting Config object.
 
         Examples
         --------
 
             >>> from IPython.config.loader import KeyValueConfigLoader
             >>> cl = KeyValueConfigLoader()
             >>> d = cl.load_config(["--A.name='brian'","--B.number=0"])
             >>> sorted(d.items())
             [('A', {'name': 'brian'}), ('B', {'number': 0})]
         """
         super(KeyValueConfigLoader, self).__init__(**kw)
         if argv is None:
             argv = sys.argv[1:]
         self.argv = argv
         self.aliases = aliases or {}
         self.flags = flags or {}
 
 
     def clear(self):
         super(KeyValueConfigLoader, self).clear()
         self.extra_args = []
 
 
     def _decode_argv(self, argv, enc=None):
         """decode argv if bytes, using stin.encoding, falling back on default enc"""
         uargv = []
         if enc is None:
             enc = DEFAULT_ENCODING
         for arg in argv:
             if not isinstance(arg, unicode_type):
                 # only decode if not already decoded
                 arg = arg.decode(enc)
             uargv.append(arg)
         return uargv
 
 
     def load_config(self, argv=None, aliases=None, flags=None):
         """Parse the configuration and generate the Config object.
 
         After loading, any arguments that are not key-value or
         flags will be stored in self.extra_args - a list of
         unparsed command-line arguments.  This is used for
         arguments such as input files or subcommands.
 
         Parameters
         ----------
         argv : list, optional
             A list that has the form of sys.argv[1:] which has unicode
             elements of the form u"key=value". If this is None (default),
             then self.argv will be used.
         aliases : dict
             A dict of aliases for configurable traits.
             Keys are the short aliases, Values are the resolved trait.
             Of the form: `{'alias' : 'Configurable.trait'}`
         flags : dict
             A dict of flags, keyed by str name. Values can be Config objects
             or dicts.  When the flag is triggered, The config is loaded as
             `self.config.update(cfg)`.
         """
         self.clear()
         if argv is None:
             argv = self.argv
         if aliases is None:
             aliases = self.aliases
         if flags is None:
             flags = self.flags
 
         # ensure argv is a list of unicode strings:
         uargv = self._decode_argv(argv)
         for idx,raw in enumerate(uargv):
             # strip leading '-'
             item = raw.lstrip('-')
 
             if raw == '--':
                 # don't parse arguments after '--'
                 # this is useful for relaying arguments to scripts, e.g.
                 # ipython -i foo.py --matplotlib=qt -- args after '--' go-to-foo.py
                 self.extra_args.extend(uargv[idx+1:])
                 break
 
             if kv_pattern.match(raw):
                 lhs,rhs = item.split('=',1)
                 # Substitute longnames for aliases.
                 if lhs in aliases:
                     lhs = aliases[lhs]
                 if '.' not in lhs:
                     # probably a mistyped alias, but not technically illegal
                     self.log.warn("Unrecognized alias: '%s', it will probably have no effect.", raw)
                 try:
                     self._exec_config_str(lhs, rhs)
                 except Exception:
                     raise ArgumentError("Invalid argument: '%s'" % raw)
 
             elif flag_pattern.match(raw):
                 if item in flags:
                     cfg,help = flags[item]
                     self._load_flag(cfg)
                 else:
                     raise ArgumentError("Unrecognized flag: '%s'"%raw)
             elif raw.startswith('-'):
                 kv = '--'+item
                 if kv_pattern.match(kv):
                     raise ArgumentError("Invalid argument: '%s', did you mean '%s'?"%(raw, kv))
                 else:
                     raise ArgumentError("Invalid argument: '%s'"%raw)
             else:
                 # keep all args that aren't valid in a list,
                 # in case our parent knows what to do with them.
                 self.extra_args.append(item)
         return self.config
 
 class ArgParseConfigLoader(CommandLineConfigLoader):
     """A loader that uses the argparse module to load from the command line."""
 
     def __init__(self, argv=None, aliases=None, flags=None, log=None,  *parser_args, **parser_kw):
         """Create a config loader for use with argparse.
 
         Parameters
         ----------
 
         argv : optional, list
           If given, used to read command-line arguments from, otherwise
           sys.argv[1:] is used.
 
         parser_args : tuple
           A tuple of positional arguments that will be passed to the
           constructor of :class:`argparse.ArgumentParser`.
 
         parser_kw : dict
           A tuple of keyword arguments that will be passed to the
           constructor of :class:`argparse.ArgumentParser`.
 
         Returns
         -------
         config : Config
             The resulting Config object.
         """
         super(CommandLineConfigLoader, self).__init__(log=log)
         self.clear()
         if argv is None:
             argv = sys.argv[1:]
         self.argv = argv
         self.aliases = aliases or {}
         self.flags = flags or {}
 
         self.parser_args = parser_args
         self.version = parser_kw.pop("version", None)
         kwargs = dict(argument_default=argparse.SUPPRESS)
         kwargs.update(parser_kw)
         self.parser_kw = kwargs
 
     def load_config(self, argv=None, aliases=None, flags=None):
         """Parse command line arguments and return as a Config object.
 
         Parameters
         ----------
 
         args : optional, list
           If given, a list with the structure of sys.argv[1:] to parse
           arguments from. If not given, the instance's self.argv attribute
           (given at construction time) is used."""
         self.clear()
         if argv is None:
             argv = self.argv
         if aliases is None:
             aliases = self.aliases
         if flags is None:
             flags = self.flags
         self._create_parser(aliases, flags)
         self._parse_args(argv)
         self._convert_to_config()
         return self.config
 
     def get_extra_args(self):
         if hasattr(self, 'extra_args'):
             return self.extra_args
         else:
             return []
 
     def _create_parser(self, aliases=None, flags=None):
         self.parser = ArgumentParser(*self.parser_args, **self.parser_kw)
         self._add_arguments(aliases, flags)
 
     def _add_arguments(self, aliases=None, flags=None):
         raise NotImplementedError("subclasses must implement _add_arguments")
 
     def _parse_args(self, args):
         """self.parser->self.parsed_data"""
         # decode sys.argv to support unicode command-line options
         enc = DEFAULT_ENCODING
         uargs = [py3compat.cast_unicode(a, enc) for a in args]
         self.parsed_data, self.extra_args = self.parser.parse_known_args(uargs)
 
     def _convert_to_config(self):
         """self.parsed_data->self.config"""
         for k, v in iteritems(vars(self.parsed_data)):
             exec("self.config.%s = v"%k, locals(), globals())
 
 class KVArgParseConfigLoader(ArgParseConfigLoader):
     """A config loader that loads aliases and flags with argparse,
     but will use KVLoader for the rest.  This allows better parsing
     of common args, such as `ipython -c 'print 5'`, but still gets
     arbitrary config with `ipython --InteractiveShell.use_readline=False`"""
 
     def _add_arguments(self, aliases=None, flags=None):
         self.alias_flags = {}
         # print aliases, flags
         if aliases is None:
             aliases = self.aliases
         if flags is None:
             flags = self.flags
         paa = self.parser.add_argument
         for key,value in iteritems(aliases):
             if key in flags:
                 # flags
                 nargs = '?'
             else:
                 nargs = None
             if len(key) is 1:
                 paa('-'+key, '--'+key, type=unicode_type, dest=value, nargs=nargs)
             else:
                 paa('--'+key, type=unicode_type, dest=value, nargs=nargs)
         for key, (value, help) in iteritems(flags):
             if key in self.aliases:
                 #
                 self.alias_flags[self.aliases[key]] = value
                 continue
             if len(key) is 1:
                 paa('-'+key, '--'+key, action='append_const', dest='_flags', const=value)
             else:
                 paa('--'+key, action='append_const', dest='_flags', const=value)
 
     def _convert_to_config(self):
         """self.parsed_data->self.config, parse unrecognized extra args via KVLoader."""
         # remove subconfigs list from namespace before transforming the Namespace
         if '_flags' in self.parsed_data:
             subcs = self.parsed_data._flags
             del self.parsed_data._flags
         else:
             subcs = []
 
         for k, v in iteritems(vars(self.parsed_data)):
             if v is None:
                 # it was a flag that shares the name of an alias
                 subcs.append(self.alias_flags[k])
             else:
                 # eval the KV assignment
                 self._exec_config_str(k, v)
 
         for subc in subcs:
             self._load_flag(subc)
 
         if self.extra_args:
             sub_parser = KeyValueConfigLoader(log=self.log)
             sub_parser.load_config(self.extra_args)
             self.config.merge(sub_parser.config)
             self.extra_args = sub_parser.extra_args
 
 
 def load_pyconfig_files(config_files, path):
     """Load multiple Python config files, merging each of them in turn.
 
     Parameters
     ==========
     config_files : list of str
         List of config files names to load and merge into the config.
     path : unicode
         The full path to the location of the config files.
     """
     config = Config()
     for cf in config_files:
         loader = PyFileConfigLoader(cf, path=path)
         try:
             next_config = loader.load_config()
         except ConfigFileNotFound:
             pass
         except:
             raise
         else:
             config.merge(next_config)
     return config