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"""

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    Miscellaneous utilities

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"""

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import functools

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class LazyProperty (property) :

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    """

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        Lazy-loaded properties

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    """

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    ATTRNAME = '_LazyProperty_values'

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    def __init__ (self, func) :

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        """

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            Initialize with no value

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        """

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        super(LazyProperty, self).__init__(func)

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        self.func = func

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        self.name = func.__name__

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        self.value = None

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    def run (self, obj) :

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        """

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            Run the background func and return the to-be-cached value

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        """

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        return self.func(obj)

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    def obj_dict (self, obj):

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        """

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            Get the lazy-property dict of the given obj

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        """

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        dict = getattr(obj, self.ATTRNAME, None)

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        if dict is None :

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            dict = {}

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            setattr(obj, self.ATTRNAME, dict)

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        return dict

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    def get (self, obj) :

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        """

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            Return the cached value

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        """

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        return self.obj_dict(obj)[self.name]

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    def set (self, obj, value) :

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        """

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            Set the cached value

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        """

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        self.obj_dict(obj)[self.name] = value

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    def test (self, obj) :

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        """

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            Tests if a value is set

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        """

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        return self.name in self.obj_dict(obj)

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    def __get__ (self, obj, owner) :

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        """

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            Return the cached value if it exists, otherwise, call the func

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        """

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        if not obj :

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            return self

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        if not self.test(obj) :

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            # generate it

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            self.set(obj, self.run(obj))

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        return self.get(obj)

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class LazyIteratorProperty (LazyProperty) :

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    """

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        A lazy-loaded property that automatically converts an iterator/genexp into a list.

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    """

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    def run (self, obj) :

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        """

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            Wrap LazyProperty.run to return a list

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        """

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        return list(super(LazyIteratorProperty, self).run(obj))

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lazy_load = LazyProperty

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lazy_load_iter = LazyIteratorProperty

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