On 2009-09-07 07:11 , Robert wrote: > Is there a reason why ndarray truth tests (except scalars) > deviates from the convention of other Python iterables > list,array.array,str,dict,... ? > > Furthermore there is a surprising strange exception for arrays > with size 1 (!= scalars).
Historically, numpy's predecessors used "not equal to zero" as the meaning for truth (consistent with numerical types in Python). However, this introduces an ambiguity as both any(a != 0) and all(a != 0) are reasonable interpretations of the truth value of a sequence of numbers. Numpy refuses to guess and raises the exception shown below. For sequences with a single item, there is no ambiguity and numpy does the (numerically) ordinary thing. The ndarray type available in Numpy is not conceptually an extension of Python's iterables. If you'd like to help other Numpy users with this issue, you can edit the documentation in the online documentation editor at http://docs.scipy.org/numpy/docs/numpy-docs/user/index.rst -Neil _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
