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Python lazy hasattr()

Python hasattr() evaluates the specified attribute, which may not be desired !

class Attr(object):
    def __get__(self, obs, cls=None):
        print "evaluated"
        return 0

class ClassA(object):
    a = Attr()

    @property
    def b(self):
        print "evaluated"
        return 0

>>> c = ClassA()
>>> c.a
evaluated
0
>>> c.b
evaluated
0

Now note that hasattr() evaluates the lazy attribute !

>>> hasattr(c, 'a')
evaluated
True
>>> hasattr(c, 'b')
evaluated
True

Let us fix that !

def lazyhasattr(obj, name):
    return any(name in d for d in (obj.__dict__,
                                   obj.__class__.__dict__))

>>> c = ClassA()
>>> lazyhasattr(c, 'a')
True
>>> lazyhasattr(c, 'b')
True

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