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Subject: Re: Multi-dimensional list initialization
From: Demian Brecht <demianbrecht@gmail.com>
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Date: Tue, 6 Nov 2012 22:56:33 -0800
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To: Steven D'Aprano <steve+comp.lang.python@pearwood.info>
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On 2012-11-06, at 5:55 PM, Steven D'Aprano =
<steve+comp.lang.python@pearwood.info> wrote:
> I'm not entirely sure what your point is here. The OP screwed up -- he=20=

> didn't generate a 4-dimensional array. He generated a 2-dimensional=20
> array. If his intuition about the number of dimensions is so poor, why=20=

> should his intuition about list multiplication be treated as =
sacrosanct?

Yep, I may have mis-worded the explanation a bit (although I *did* =
express that it was a 4D matrix in the OP). I was using a 2D list to =
represent a 4D matrix in order to easily iterate over 90 degree =
rotations with zip(*matrix[::-1]). It wasn't for production code =
(otherwise I *would* be using numpy), it was for an online programming =
challenge in which external libs are not supported.

> As they say, the only truly intuitive interface is the nipple. There =
are=20
> many places where people's intuition about programming fail. And many=20=

> places where Fred's intuition is the opposite of Barney's intuition.

I couldn't agree more with this. My question was *not* based on what I =
perceive to be intuitive (although most of this thread has now seemed to =
devolve into that and become more of a philosophical debate), but was =
based on what I thought may have been inconsistent behaviour (which was =
quickly cleared up with None being immutable and causing it to *seem* =
that the behaviour was inconsistent to the forgetful mind). As you touch =
on here, "intuition" is entirely subjective. If you're coming from a =
C/C++ background, I'd think that your intuition would be that =
everything's passed by value unless explicitly stated. Someone coming =
from another background (Lua perhaps?) would likely have entirely =
different intuition.

> So while I prefer intuitively obvious behaviour where possible, it is =
not=20
> the holy grail, and I am quite happy to give it up.

I fail to see where there has been any giving up on intuitiveness in the =
context of this particular topic. In my mind, intuitiveness is generally =
born of repetitiveness and consistency. As everything in Python is a =
reference, it would seem to me to be inconsistent to treat expressions =
such as [[obj]*4]*4 un-semantically (Pythonically speaking) and making =
it *less* intuitive. I agree that Python would definitely be worse off.

Demian Brecht
@demianbrecht
http://demianbrecht.github.com