1# Copyright 2020 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"""Thread-local stack.""" 16 17from __future__ import absolute_import 18from __future__ import division 19from __future__ import print_function 20 21import threading 22 23 24# TODO(srbs): Move this to C++. 25class ThreadLocalStack(threading.local): 26 """A thread-local stack of objects for providing implicit defaults.""" 27 28 def __init__(self): 29 super(ThreadLocalStack, self).__init__() 30 self._stack = [] 31 32 def peek(self): 33 return self._stack[-1] if self._stack else None 34 35 def push(self, ctx): 36 return self._stack.append(ctx) 37 38 def pop(self): 39 self._stack.pop() 40