Duck typing is great and all for classes that implement some or all of the ndarray interface.... but remember what the main reason for asarray() and asanyarray(): to automatically promote lists and tuples and other "array-likes" to ndarrays. Ignoring the use-case of lists of lists is problematic at best.

Ben Root

On Thu, Nov 2, 2017 at 5:05 PM, Marten van Kerkwijk <> wrote:
My 2ยข here is that all code should feel free to assume certain type of
input, as long as it is documented properly, but there is no reason to
enforce that by, e.g., putting `asarray` everywhere. Then, for some
pieces ducktypes and subclasses will just work like magic, and uses
you might never have foreseen become possible. For others, whoever
wants to use them has to do work (and up to a package maintainers to
decide whether or not to accept PRs that implement hooks, etc.)

I do see the argument that this way one becomes constrained in the
internal implementation, as a change may break an outward-looking
function, but while at times this may be inconvenient, in my
experience at others it may just make one realize an even better
implementation is possible. But then, I really like duck-typing...

-- Marten
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