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# Copyright 2012 OpenStack Foundation
#
# 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 os
class HookableMixin(object):
"""Mixin so classes can register and run hooks."""
_hooks_map = {}
@classmethod
def add_hook(cls, hook_type, hook_func):
if hook_type not in cls._hooks_map:
cls._hooks_map[hook_type] = []
cls._hooks_map[hook_type].append(hook_func)
@classmethod
def run_hooks(cls, hook_type, *args, **kwargs):
hook_funcs = cls._hooks_map.get(hook_type) or []
for hook_func in hook_funcs:
hook_func(*args, **kwargs)
def env(*vars, **kwargs):
"""Returns environment variables.
Returns the first environment variable set
if none are non-empty, defaults to '' or keyword arg default.
"""
for v in vars:
value = os.environ.get(v, None)
if value:
return value
return kwargs.get('default', '')
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