56 lines
2.4 KiB
Python
56 lines
2.4 KiB
Python
# Copyright (c) 2010 Google 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 are
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# met:
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#
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# * 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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# * Redistributions in binary form must reproduce the above
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# copyright notice, this list of conditions and the following disclaimer
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# in the documentation and/or other materials provided with the
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# distribution.
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# * Neither the name of Google Inc. nor the names of its
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# contributors may be used to endorse or promote products derived from
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# this software without specific prior written permission.
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#
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# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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# THEORY 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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# Python does not (yet) seem to provide automatic memoization. So we've
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# written a small decorator to do so.
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import functools
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class memoized(object):
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def __init__(self, function):
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self._function = function
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self._results_cache = {}
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def __call__(self, *args):
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try:
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return self._results_cache[args]
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except KeyError:
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# If we didn't find the args in our cache, call and save the results.
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result = self._function(*args)
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self._results_cache[args] = result
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return result
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# FIXME: We may need to handle TypeError here in the case
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# that "args" is not a valid dictionary key.
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# Use python "descriptor" protocol __get__ to appear
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# invisible during property access.
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def __get__(self, instance, owner):
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# Return a function partial with obj already bound as self.
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return functools.partial(self.__call__, instance)
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