Dan Goodman wrote: > Hi all, > > I think this is a bug (I'm running Numpy 1.0.3.1): > >>>> from numpy import * >>>> def f(x): return False > >>>> all(f(x) for x in range(10)) > True > > I guess the all function doesn't know about generators?
Yup. It works on arrays and things it can turn into arrays by calling the C API equivalent of numpy.asarray(). There's a ton of magic and special cases in asarray() in order to interpret nested Python sequences as arrays. That magic works fairly well when we have sequences with known lengths; it fails utterly when given an arbitrary iterator of unknown length. So we punt. Unfortunately, what happens then is that asarray() sees an object that it can't interpret as a sequence to turn into a real array, so it makes a rank-0 array with the iterator object as the value. This evaluates to True. It's possible that asarray() should raise an exception for generators, but it would be a special case. We wouldn't be able to test for arbitrary iterables. -- Robert Kern "I have come to believe that the whole world is an enigma, a harmless enigma that is made terrible by our own mad attempt to interpret it as though it had an underlying truth." -- Umberto Eco _______________________________________________ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
