On Wed, 2023-03-22 at 12:00 -0400, Robert Kern wrote: > On Wed, Mar 22, 2023 at 9:34 AM Neal Becker <ndbeck...@gmail.com> > wrote: > > > I have a function F > > def F(a, b): > > c = a * b > > > > Initially, a is a scalar, b[240,3000]. No problem. > > Later I want to use F, where a[240] is a vector. I want to allow > > both the > > scalar and vector cases. So I write: > > > > def F(a,b): > > a = np.atleast_1d(a) > > c = a[:,None] * b > > > > This now works for scalar a or vector a. But this solutions seems > > inelegant, and somewhat fragile. Suppose later we want to allow > > a[240,3000], a 2d array matching b. > > > > Certainly don't want to write code like: > > if a.ndim == 0:... > > > > Is there a more elegant/robust approach? > > > > I would leave it as `c = a * b` and simply record in the docstring > that `a` > and `b` should be broadcastable. Yes, that means that the user will > have to > write `F(a[:, np.newaxis], b)` for that one case, and that looks a > little > ugly, but overall it's less cognitive load on the user to just reuse > the > common convention of broadcasting than to record the special case.
I will note that it is not hard to insert the new axes. `np.expand_dims` may be convenient. many functions (ufuncs) also have the `outer` version which does this: `np.add.outer()`, etc. However, I agree. Unless the use-case exceedingly clear about requiring "outer" behavior. "outer" behavior is uncommon for functions in the NumPy world and broadcasting is what users will generally expect (and that includes future self). - Sebastian > > _______________________________________________ > NumPy-Discussion mailing list -- numpy-discussion@python.org > To unsubscribe send an email to numpy-discussion-le...@python.org > https://mail.python.org/mailman3/lists/numpy-discussion.python.org/ > Member address: sebast...@sipsolutions.net _______________________________________________ NumPy-Discussion mailing list -- numpy-discussion@python.org To unsubscribe send an email to numpy-discussion-le...@python.org https://mail.python.org/mailman3/lists/numpy-discussion.python.org/ Member address: arch...@mail-archive.com
