| # Copyright 2015, Google Inc. |
| # All rights reserved. |
| # |
| # Redistribution and use in source and binary forms, with or without |
| # modification, are permitted provided that the following conditions are |
| # met: |
| # |
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| # notice, this list of conditions and the following disclaimer. |
| # * Redistributions in binary form must reproduce the above |
| # copyright notice, this list of conditions and the following disclaimer |
| # in the documentation and/or other materials provided with the |
| # distribution. |
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| # contributors may be used to endorse or promote products derived from |
| # this software without specific prior written permission. |
| # |
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| |
| """Interfaces related to streams of values or objects.""" |
| |
| import abc |
| |
| import six |
| |
| class Activated(six.with_metaclass(abc.ABCMeta)): |
| """Interface for objects that may be started and stopped. |
| |
| Values implementing this type must also implement the context manager |
| protocol. |
| """ |
| |
| @abc.abstractmethod |
| def __enter__(self): |
| """See the context manager protocol for specification.""" |
| raise NotImplementedError() |
| |
| @abc.abstractmethod |
| def __exit__(self, exc_type, exc_val, exc_tb): |
| """See the context manager protocol for specification.""" |
| raise NotImplementedError() |
| |
| @abc.abstractmethod |
| def start(self): |
| """Activates this object. |
| |
| Returns: |
| A value equal to the value returned by this object's __enter__ method. |
| """ |
| raise NotImplementedError() |
| |
| @abc.abstractmethod |
| def stop(self): |
| """Deactivates this object.""" |
| raise NotImplementedError() |