[Numpy-discussion] ndarray.T2 for 2D transpose

Ian Henriksen insertinterestingnamehere at gmail.com
Thu Apr 7 13:00:33 EDT 2016


On Wed, Apr 6, 2016 at 3:21 PM Nathaniel Smith <njs at pobox.com> wrote:

> Can you elaborate on what you're doing that you find verbose and
> confusing, maybe paste an example? I've never had any trouble like
> this doing linear algebra with @ or dot (which have similar semantics
> for 1d arrays), which is probably just because I've had different use
> cases, but it's much easier to talk about these things with a concrete
> example in front of us to put everyone on the same page.
>
> -n
>

Here's another example that I've seen catch people now and again.

A = np.random.rand(100, 100)
b =  np.random.rand(10)
A * b.T

In this case the user pretty clearly meant to be broadcasting along the
rows of A
rather than along the columns, but the code fails silently. When an issue
like this
gets mixed into a larger series of broadcasting operations, the error
becomes
difficult to find. This error isn't necessarily unique to beginners either.
It's a
common typo that catches intermediate users who know about broadcasting
semantics but weren't keeping close enough track of the dimensionality of
the
different intermediate expressions in their code.

Best,

-Ian Henriksen
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