what is this?

Huayang Xia huayang.xia at gmail.com
Thu Jan 4 18:02:28 CET 2007


Sequence slicing [starting-at-index :  but-less-than-index [ : step]].
Start defaults to 0, end to len(sequence), step to 1.
So l[i::rows] means: slicing start from i, ending with len(l) and step
with rows. So function colsplit(l, cols) returns a list of sequence
with conversion of:

Assume cols = 4:
From:

ABCD
ABCD
ABCD
AB

To:
AAAABBBBCCCDDD



On Jan 4, 11:42 am, "Eric Price"
<soyouthinkimgonnaliket... at hotmail.com> wrote:
> Hello;
> I'm studying some code examples from the python cookbook site. I came across
> this:
>
> def colsplit(l, cols):
>     rows = len(l) / cols
>     if len(l) % cols:
>         rows += 1
>     m = []
>     for i in range(rows):
>         m.append(l[i::rows])
>     return m
>
> What I'd like to know is what is the double colon? What does it do?
>         m.append(l[i::rows])
>
> Thanks,
> Eric
>
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