Silly question

Duncan Booth duncan.booth at invalid.invalid
Thu Aug 20 20:41:34 CEST 2009


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. 



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