Perry Greenfield wrote:

We've noticed that in numpy that the where() function behaves differently than for numarray. In numarray, where() (when used with a mask or condition array only) always returns a tuple of index arrays, even for the 1D case whereas numpy returns an index array for the 1D case and a tuple for higher dimension cases. While the tuple is a annoyance for users when they want to manipulate the 1D case, the benefit is that one always knows that where is returning a tuple, and thus can write code accordingly. The problem with the current numpy behavior is that it requires special case testing to see which kind return one has before manipulating if you aren't certain of what the dimensionality of the argument is going to be.

I think this is reasonable. I don't think much thought went in to the current behavior as it simply defaults to the behavior of the nonzero method (where just defaults to nonzero in the circumstances you are describing). The nonzero method has it's behavior because of the nonzero function in Numeric (which only worked with 1-d and returned an array not a tuple). Ideally, I think we should fix the nonzero method and where to have the same behavior (both return tuples --- that's actually what the docstring of nonzero says right now). The nonzero function can be special-cased to index the tuple for backward compatibility. -Travis