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1 ### -*- coding: utf-8 -*- #################################################### |
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2 ############################################################################## |
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3 # |
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4 # Copyright (c) 2012 Thierry Florac <tflorac AT ulthar.net> |
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5 # All Rights Reserved. |
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6 # |
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7 # This software is subject to the provisions of the Zope Public License, |
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8 # Version 2.1 (ZPL). A copy of the ZPL should accompany this distribution. |
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9 # THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED |
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10 # WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED |
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11 # WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS |
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12 # FOR A PARTICULAR PURPOSE. |
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13 # |
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14 ############################################################################## |
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15 |
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16 |
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17 # import standard packages |
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18 |
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19 # import Zope3 interfaces |
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20 |
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21 # import local interfaces |
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22 |
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23 # import Zope3 packages |
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24 |
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25 # import local packages |
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26 |
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27 |
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28 class cached(object): |
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29 """Custom property decorator to define a property or function |
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30 which is calculated only once |
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31 |
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32 When applied on a function, caching is based on input arguments |
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33 """ |
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34 |
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35 def __init__(self, function): |
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36 self._function = function |
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37 self._cache = {} |
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38 |
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39 def __call__(self, *args): |
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40 try: |
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41 return self._cache[args] |
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42 except KeyError: |
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43 self._cache[args] = self._function(*args) |
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44 return self._cache[args] |
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45 |
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46 def expire(self, *args): |
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47 del self._cache[args] |
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48 |
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49 |
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50 class cached_property(object): |
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51 """A read-only @property decorator that is only evaluated once. The value is cached |
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52 on the object itself rather than the function or class; this should prevent |
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53 memory leakage. |
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54 """ |
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55 def __init__(self, fget, doc=None): |
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56 self.fget = fget |
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57 self.__doc__ = doc or fget.__doc__ |
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58 self.__name__ = fget.__name__ |
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59 self.__module__ = fget.__module__ |
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60 |
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61 def __get__(self, obj, cls): |
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62 if obj is None: |
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63 return self |
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64 obj.__dict__[self.__name__] = result = self.fget(obj) |
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65 return result |