Silly question

David C Ullrich dullrich at sprynet.com
Thu Aug 20 21:31:30 CEST 2009


On Thu, 20 Aug 2009 18:41:34 +0000, Duncan Booth wrote:

> David C Ullrich <dullrich at sprynet.com> wrote:
> 
>> I just noticed that
>> 
>>   sequence[i:j:k]
>> 
>> syntax in a post here. When did this happen?
>> 
>> (I'm just curious whether it existed in 1.5.x or not. If so I'm stupid
>> - otoh if it was introduced in 2.x I'm just slow...)
>> 
>> 
> Googling for 'python extended slice' returns this as the first hit:
> 
> http://www.python.org/doc/2.3.5/whatsnew/section-slices.html
> 
>> 15 Extended Slices
>> 
>> Ever since Python 1.4, the slicing syntax has supported an optional
>> third ``step'' or ``stride'' argument. For example, these are all legal
>> Python syntax: L[1:10:2], L[:-1:1], L[::-1]. This was added to Python
>> at the request of the developers of Numerical Python, which uses the
>> third argument extensively. However, Python's built-in list, tuple, and
>> string sequence types have never supported this feature, raising a
>> TypeError if you tried it. Michael Hudson contributed a patch to fix
>> this shortcoming.
> 
> So extended slices have existed since Python 1.4, but builtin types only
> started to support them from 2.3.

Fine (I knew they existed in Numerical Python way back when...)





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