Re: [Numpy-discussion] questions regarding assignement and copy

[Christopher B. <Chr...@no...>]

Robert Kern wrote:
>  From the reference manual:
> 
> http://docs.python.org/ref/augassign.html
> 
> """An augmented assignment expression like x += 1 can be rewritten as x = x + 1 
> to achieve a similar, but not exactly equal effect. In the augmented version, x 
> is only evaluated once. Also, when possible, the actual operation is performed 
> in-place, meaning that rather than creating a new object and assigning that to 
> the target, the old object is modified instead."""

I've always thought this was a mistake -- it is a source of weird errors 
and bugs. AFAIC, the augmented assignments should ONLY work with mutable 
objects, and ALWAYS do the operation in place.

But then you couldn't write:

i = 1
i += 1

Because python numbers are immutable. I think the problem here is that 
augmented assignment is solving two distinct problems: in place 
operations and nice syntax for incrementing.

Oh well, it's not that big a deal, and usually the confusion causes 
errors that show up right away.

-Chris


-- 
Christopher Barker, Ph.D.
Oceanographer
                                     		
NOAA/OR&R/HAZMAT         (206) 526-6959   voice
7600 Sand Point Way NE   (206) 526-6329   fax
Seattle, WA  98115       (206) 526-6317   main reception

Chr...@no...