69 lines
2.2 KiB
Python
69 lines
2.2 KiB
Python
# vim: tabstop=4 shiftwidth=4 softtabstop=4
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# Copyright 2011 OpenStack Foundation.
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# All Rights Reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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"""
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Import related utilities and helper functions.
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"""
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import sys
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import traceback
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def import_class(import_str):
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"""Returns a class from a string including module and class."""
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mod_str, _sep, class_str = import_str.rpartition('.')
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try:
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__import__(mod_str)
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return getattr(sys.modules[mod_str], class_str)
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except (ValueError, AttributeError):
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raise ImportError('Class %s cannot be found (%s)' %
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(class_str,
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traceback.format_exception(*sys.exc_info())))
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def import_object(import_str, *args, **kwargs):
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"""Import a class and return an instance of it."""
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return import_class(import_str)(*args, **kwargs)
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def import_object_ns(name_space, import_str, *args, **kwargs):
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"""Tries to import object from default namespace.
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Imports a class and return an instance of it, first by trying
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to find the class in a default namespace, then failing back to
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a full path if not found in the default namespace.
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"""
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import_value = "%s.%s" % (name_space, import_str)
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try:
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return import_class(import_value)(*args, **kwargs)
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except ImportError:
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return import_class(import_str)(*args, **kwargs)
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def import_module(import_str):
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"""Import a module."""
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__import__(import_str)
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return sys.modules[import_str]
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def try_import(import_str, default=None):
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"""Try to import a module and if it fails return default."""
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try:
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return import_module(import_str)
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except ImportError:
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return default
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