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#==========================================================================
#
# Copyright Insight Software Consortium
#
# 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.txt
#
# 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 types
import itkBase
not_loaded = 'not loaded'
class LazyITKModule(types.ModuleType):
"""Subclass of ModuleType that implements a custom __getattribute__ method
to allow lazy-loading of attributes from ITK sub-modules."""
def __init__(self, name, lazy_attributes):
types.ModuleType.__init__(self, name)
self.__lazy_attributes = lazy_attributes
for k in lazy_attributes:
setattr(self, k, not_loaded)
def __getattribute__(self, attr):
value = types.ModuleType.__getattribute__(self, attr)
if value is not_loaded:
module = self.__lazy_attributes[attr]
namespace = {}
itkBase.LoadModule(module, namespace)
# Load into 'namespace' first, then self.__dict__ (via setattr) to
# prevent the warnings about overwriting the 'NotLoaded' values
# already in self.__dict__ we would get if we just passed
# self.__dict__ to itkBase.LoadModule.
for k, v in namespace.items():
setattr(self, k, v)
value = namespace[attr]
return value
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