[Numpy-discussion] copy="never" discussion and no deprecation cycle?

Benjamin Root ben.v.root at gmail.com
Wed Jun 23 22:26:16 EDT 2021

> One reason was that Sebastian didn't like people doing `x.shape = ...`.
> Users do that, presumably, to trigger an error if a copy needs to be made.

Users do that because it is 1) easier than every other option, and 2) I am
pretty sure we were encouraged to do it this way for the past 10 years. The
whole "it won't copy" business (to me at least) was an added bonus. Most of
the time, I didn't want to copy anyway, so, sure!

`x.shape = ...` has been around for a long time, and you are going to have
a hard time convincing people to drop using such an easy-to-use property
setter in favor of an approach that adds more typing and takes a bit more
to read. There's also lots and lots of online tutorials, books, and
stackoverflow snippets that have this usage pattern. I think the horse has
long since left the barn, the chickens came to roost, and the cows came

> We can fix Sebastian's issue by introducing a `copy` keyword to `reshape`,
> which currently has none:
This isn't a terrible idea to pursue, regardless of what I said above!
Explicit is better than implicit, and giving programmers the opportunity to
be explicit about what sort of copy semantics they intend in more places
would improve the library going forward.  I also like to highlight what
Chuck said a few posts ago about the fact that `copy=False` does not really
mean what people might think it means, and taking steps to address that
might also be good for the library.

Ben Root
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