65 lines
1.9 KiB
Python
65 lines
1.9 KiB
Python
class cached_property(object):
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"""Property descriptor that caches the return value
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of the get function.
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*Examples*
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.. code-block:: python
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@cached_property
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def connection(self):
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return Connection()
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@connection.setter # Prepares stored value
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def connection(self, value):
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if value is None:
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raise TypeError("Connection must be a connection")
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return value
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@connection.deleter
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def connection(self, value):
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# Additional action to do at del(self.attr)
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if value is not None:
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print("Connection %r deleted" % (value, ))
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"""
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def __init__(self, fget=None, fset=None, fdel=None, doc=None):
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self.__get = fget
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self.__set = fset
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self.__del = fdel
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self.__doc__ = doc or fget.__doc__
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self.__name__ = fget.__name__
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self.__module__ = fget.__module__
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def __get__(self, obj, type=None):
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if obj is None:
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return self
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try:
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return obj.__dict__[self.__name__]
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except KeyError:
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value = obj.__dict__[self.__name__] = self.__get(obj)
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return value
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def __set__(self, obj, value):
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if obj is None:
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return self
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if self.__set is not None:
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value = self.__set(obj, value)
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obj.__dict__[self.__name__] = value
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def __delete__(self, obj):
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if obj is None:
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return self
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try:
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value = obj.__dict__.pop(self.__name__)
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except KeyError:
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pass
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else:
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if self.__del is not None:
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self.__del(obj, value)
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def setter(self, fset):
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return self.__class__(self.__get, fset, self.__del)
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def deleter(self, fdel):
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return self.__class__(self.__get, self.__set, fdel)
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