what is this?

[Paul Watson]

Paul Watson wrote:
> Eric Price 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
> 
> http://docs.python.org/tut/tut.html
> http://docs.python.org/tut/node5.html#SECTION005140000000000000000
> http://docs.python.org/ref/slicings.html
> 
> Probably most helpful to you is:
> 
> http://developer.mozilla.org/es4/proposals/slice_syntax.html

Sorry.  Probably most helpful to you is:

http://docs.python.org/lib/built-in-funcs.html

slice(  	[start,] stop[, step])
     Return a slice object representing the set of indices specified by 
range(start, stop, step). The start and step arguments default to None. 
Slice objects have read-only data attributes start, stop and step which 
merely return the argument values (or their default). They have no other 
explicit functionality; however they are used by Numerical Python and 
other third party extensions. Slice objects are also generated when 
extended indexing syntax is used. For example: "a[start:stop:step]" or 
"a[start:stop, i]".