text: # Copyright 2011 OpenStack Foundation.
  # All Rights Reserved.
  #
  #    Licensed under the Apache License, Version 2.0 (the "License"); you may
  #    not use this file except in compliance with the License. You may obtain
  #    a copy of the License at
  #
  #         http://www.apache.org/licenses/LICENSE-2.0
  #
  #    Unless required by applicable law or agreed to in writing, software
  #    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
  #    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
  #    License for the specific language governing permissions and limitations
  #    under the License.
  
  """
  Import related utilities and helper functions.
  """
  
  import sys
  import traceback
  
  
  def import_class(import_str):
      """Returns a class from a string including module and class."""
      mod_str, _sep, class_str = import_str.rpartition('.')
      __import__(mod_str)
      try:
          return getattr(sys.modules[mod_str], class_str)
      except AttributeError:
          raise ImportError('Class %s cannot be found (%s)' %
                            (class_str,
                             traceback.format_exception(*sys.exc_info())))
  
  
  def import_object(import_str, *args, **kwargs):
      """Import a class and return an instance of it."""
      return import_class(import_str)(*args, **kwargs)
  
  
  def import_object_ns(name_space, import_str, *args, **kwargs):
      """Tries to import object from default namespace.
  
      Imports a class and return an instance of it, first by trying
      to find the class in a default namespace, then failing back to
      a full path if not found in the default namespace.
      """
      import_value = "%s.%s" % (name_space, import_str)
      try:
          return import_class(import_value)(*args, **kwargs)
      except ImportError:
          return import_class(import_str)(*args, **kwargs)
  
  
  def import_module(import_str):
      """Import a module."""
      __import__(import_str)
      return sys.modules[import_str]
  
  
  def import_versioned_module(version, submodule=None):
      module = 'brick.v%s' % version
      if submodule:
          module = '.'.join((module, submodule))
      return import_module(module)
  
  
  def try_import(import_str, default=None):
      """Try to import a module and if it fails return default."""
      try:
          return import_module(import_str)
      except ImportError:
          return default
  