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# 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 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
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