John Ladasky wrote: > On Friday, January 17, 2014 6:16:28 PM UTC-8, duncan smith wrote: > >> >>> a = np.arange(10) >> >>> c = np.where((2 < a) & (a < 7)) >> >>> c >> (array([3, 4, 5, 6]),) > > Nice! Thanks! > > Now, why does the multiple comparison fail, if you happen to know?
2 < a < 7 is equivalent to 2 < a and a < 7 Unlike `&` `and` cannot be overridden (*), so the above implies that the boolean value bool(2 < a) is evaluated. That triggers the error because the numpy authors refused to guess -- and rightly so, as both implementable options would be wrong in a common case like yours. (*) I assume overriding would collide with short-cutting of boolean expressions. -- https://mail.python.org/mailman/listinfo/python-list
