1 # Copyright 2015 The TensorFlow Authors. All Rights Reserved. 2 # 3 # Licensed under the Apache License, Version 2.0 (the "License"); 4 # you may not use this file except in compliance with the License. 5 # You may obtain a copy of the License at 6 # 7 # http://www.apache.org/licenses/LICENSE-2.0 8 # 9 # Unless required by applicable law or agreed to in writing, software 10 # distributed under the License is distributed on an "AS IS" BASIS, 11 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 # See the License for the specific language governing permissions and 13 # limitations under the License. 14 # ============================================================================== 15 16 """A LazyLoader class.""" 17 18 from __future__ import absolute_import 19 from __future__ import division 20 from __future__ import print_function 21 22 import importlib 23 import types 24 25 26 class LazyLoader(types.ModuleType): 27 """Lazily import a module, mainly to avoid pulling in large dependencies. 28 29 `contrib`, and `ffmpeg` are examples of modules that are large and not always 30 needed, and this allows them to only be loaded when they are used. 31 """ 32 33 # The lint error here is incorrect. 34 def __init__(self, local_name, parent_module_globals, name): # pylint: disable=super-on-old-class 35 self._local_name = local_name 36 self._parent_module_globals = parent_module_globals 37 38 super(LazyLoader, self).__init__(name) 39 40 def _load(self): 41 # Import the target module and insert it into the parent's namespace 42 module = importlib.import_module(self.__name__) 43 self._parent_module_globals[self._local_name] = module 44 45 # Update this object's dict so that if someone keeps a reference to the 46 # LazyLoader, lookups are efficient (__getattr__ is only called on lookups 47 # that fail). 48 self.__dict__.update(module.__dict__) 49 50 return module 51 52 def __getattr__(self, item): 53 module = self._load() 54 return getattr(module, item) 55 56 def __dir__(self): 57 module = self._load() 58 return dir(module) 59
