The .data attribute is generated on the fly when accessed. So it returns an anonymous temporary that's deallocated as soon as it's no longer needed.
a.data is b.data needs both objects, so both get allocated and then compared. In the second one though, each object gets allocated one at a time and then immediately released. So the a.data and b.data objects are different... but since they have non-overlapping lifetimes, they happen to be out at the same memory location. id() is only guaranteed to be unique while the object is alive. Notice also: a.data is a.data -> False -n On 6 Sep 2013 17:21, "James Bergstra" <bergs...@iro.umontreal.ca> wrote: > Hi, could someone help me understand why this assertion fails? > > def test_is(self): > a = np.empty(1) > b = np.empty(1) > if a.data is not b.data: > assert id(a.data) != id(b.data) # <-- fail > > I'm trying to write an alternate may_share_memory function. > > Thanks, > - James > > > _______________________________________________ > NumPy-Discussion mailing list > NumPy-Discussion@scipy.org > http://mail.scipy.org/mailman/listinfo/numpy-discussion > >
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