55 lines
2.1 KiB
Python
55 lines
2.1 KiB
Python
#!/usr/bin/env python
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# -*- coding: utf-8 -*-
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#
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# Copyright (C) 2019 Apple Inc. All rights reserved.
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#
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# Redistribution and use in source and binary forms, with or without
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# modification, are permitted provided that the following conditions
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# are met:
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#
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# 1. Redistributions of source code must retain the above copyright
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# notice, this list of conditions and the following disclaimer.
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# 2. Redistributions in binary form must reproduce the above copyright
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# notice, this list of conditions and the following disclaimer in the
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# documentation and/or other materials provided with the distribution.
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#
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# THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
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# EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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# PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
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# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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# EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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# PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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# PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
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# OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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# Context Manager for saving the value of an object's attribute, setting it to
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# a new value (None, by default), and then restoring the original value.
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#
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# Used as:
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#
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# myObject.fooAttribute = 1
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# print(myObject.fooAttribute)
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# with AttributeSaver(myObject, "fooAttribute", 5):
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# print(myObject.fooAttribute)
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# print(myObject.fooAttribute)
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#
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# Prints: 1, 5, 1
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class AttributeSaver:
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def __init__(self, obj, attribute, value=None):
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self.obj = obj
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self.attribute = attribute
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self.old_value = getattr(self.obj, self.attribute)
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self.new_value = value
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def __enter__(self):
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setattr(self.obj, self.attribute, self.new_value)
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def __exit__(self, exc_type, exc_value, traceback):
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setattr(self.obj, self.attribute, self.old_value)
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return None
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