content: # encoding: utf-8
  """A simple configuration system."""
  
  # Copyright (c) IPython Development Team.
  # Distributed under the terms of the Modified BSD License.
  
  import argparse
  import copy
  import logging
  import os
  import re
  import sys
  import json
  from ast import literal_eval
  
  from ipython_genutils.path import filefind
  from ipython_genutils import py3compat
  from ipython_genutils.encoding import DEFAULT_ENCODING
  from ipython_genutils.py3compat import unicode_type, iteritems
  from traitlets.traitlets import HasTraits, List, Any
  
  #-----------------------------------------------------------------------------
  # 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 collisions(self, other):
          """Check for collisions between two config objects.
          
          Returns a dict of the form {"Class": {"trait": "collision message"}}`,
          indicating which values have been ignored.
          
          An empty dict indicates no collisions.
          """
          collisions = {}
          for section in self:
              if section not in other:
                  continue
              mine = self[section]
              theirs = other[section]
              for key in mine:
                  if key in theirs and mine[key] != theirs[key]:
                      collisions.setdefault(section, {})
                      collisions[section][key] = "%r ignored, using %r" % (mine[key], theirs[key])
          return collisions
      
      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):
          new_config = type(self)()
          for key, value in self.items():
              if isinstance(value, (Config, LazyConfigValue)):
                  # deep copy config objects
                  value = copy.deepcopy(value, memo)
              elif type(value) in {dict, list, set, tuple}:
                  # shallow copy plain container traits
                  value = copy.copy(value)
              new_config[key] = value
          return new_config
      
      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 traitlets.log import get_logger
          return get_logger()
  
      def __init__(self, log=None):
          """A base class for config loaders.
  
          log : instance of :class:`logging.Logger` to use.
                By default loger of :meth:`traitlets.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.warning("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 load_subconfig(self, fname, path=None):
          """Injected into config file namespace as load_subconfig"""
          if path is None:
              path = self.path
          
          loader = self.__class__(fname, path)
          try:
              sub_config = loader.load_config()
          except ConfigFileNotFound:
              # Pass silently if the sub config is not there,
              # treat it as an empty config file.
              pass
          else:
              self.config.merge(sub_config)
      
      def _read_file_as_dict(self):
          """Load the config file into self.config, with recursive loading."""
          def get_config():
              """Unnecessary now, but a deprecation warning is more trouble than it's worth."""
              return self.config
          
          namespace = dict(
              c=self.config,
              load_subconfig=self.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 literal_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 = literal_eval(rhs)
          except (NameError, SyntaxError, ValueError):
              # 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 traitlets.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 stdin.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.warning("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
  