A bug?

[Rustom Mody]

On Tuesday, October 28, 2014 6:56:10 AM UTC+5:30, Chris Angelico wrote:
> On Tue, Oct 28, 2014 at 12:12 PM, Rustom Mody  wrote:
> > More generally for d being a 2-D reshape of dd (which may be anything
> > as long as the size matches)
> >
> >>>> dd = [1,2,3,4,5,6,7,8,9,10,11,12]
> >>>> d=[[dd[i*3+j] for j in range(3)] for i in range(4)]
> >>>> d
> > [[1, 2, 3], [4, 5, 6], [7, 8, 9], [10, 11, 12]]
> 
> The inner comprehension should surely be a slice:
> 
> >>> [dd[i*3:i*3+3] for i in range(4)]
> [[1, 2, 3], [4, 5, 6], [7, 8, 9], [10, 11, 12]]

Sweet!
[Something for my class today]

Looks even better this way:

>>> dd = range(1,13)
>>> [dd[i*3:i*3+3] for i in range(4)]
[range(1, 4), range(4, 7), range(7, 10), range(10, 13)]
>>> 

In the same vein a transpose:
>>> [list(dd[i::3]) for i in range(3)]
[[0, 3, 6, 9], [1, 4, 7, 10], [2, 5, 8, 11]]

[Not sure why both are 3; no 4's...]