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# borrowed from jaraco.util.dictlib
class NonDataProperty(object):
"""Much like the property builtin, but only implements __get__,
making it a non-data property, and can be subsequently reset.
See http://users.rcn.com/python/download/Descriptor.htm for more
information.
>>> class X(object):
... @NonDataProperty
... def foo(self):
... return 3
>>> x = X()
>>> x.foo
3
>>> x.foo = 4
>>> x.foo
4
"""
def __init__(self, fget):
assert fget is not None, "fget cannot be none"
assert callable(fget), "fget must be callable"
self.fget = fget
def __get__(self, obj, objtype=None):
if obj is None:
return self
return self.fget(obj)
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