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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.
.. versionadded:: 0.3
"""
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.
.. versionadded:: 0.3
"""
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.
.. versionadded:: 0.3
.. versionchanged:: 2.6
Don't capture :exc:`ImportError` when instanciating the object, only
when importing the object class.
"""
import_value = "%s.%s" % (name_space, import_str)
try:
cls = import_class(import_value)
except ImportError:
cls = import_class(import_str)
return cls(*args, **kwargs)
def import_module(import_str):
"""Import a module.
.. versionadded:: 0.3
"""
__import__(import_str)
return sys.modules[import_str]
def import_versioned_module(module, version, submodule=None):
"""Import a versioned module in format {module}.v{version][.{submodule}].
:param module: the module name.
:param version: the version number.
:param submodule: the submodule name.
:raises ValueError: For any invalid input.
.. versionadded:: 0.3
.. versionchanged:: 3.17
Added *module* parameter.
"""
# NOTE(gcb) Disallow parameter version include character '.'
if '.' in '%s' % version:
raise ValueError("Parameter version shouldn't include character '.'.")
module_str = '%s.v%s' % (module, version)
if submodule:
module_str = '.'.join((module_str, submodule))
return import_module(module_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
def import_any(module, *modules):
"""Try to import a module from a list of modules.
:param modules: A list of modules to try and import
:returns: The first module found that can be imported
:raises ImportError: If no modules can be imported from list
.. versionadded:: 3.8
"""
for module_name in (module,) + modules:
imported_module = try_import(module_name)
if imported_module:
return imported_module
raise ImportError('Unable to import any modules from the list %s' %
str(modules))
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