[Python-ideas] Why don't CPython strings implement slicing using a view?

[M.-A. Lemburg]

On 08.05.2015 00:09, Neil Girdhar wrote:
> This was a CPython idea after all, so I was assuming a C implementation,
> which means that new flags would have to be added to the string object to
> denote a string slice, etc.
> 
> Like I said in another message: it's not that important to me though.  I
> was just curious as to why CPython was designed so that string slicing is
> linear rather than constant time given that strings are constant.

This was considered very early on in the Unicode type design, but
dropped since the problem with such slices is that you have to keep
a reference to the original string around which keeps this alive,
even if you just use a slice of a few chars from it.

There are some situations where such a slicing mechanism
would be nice to have, but in most of those you can simply
work on the original string using an offset index.

Indeed, working with index tuples into the original string
is often a better strategy.

You can see this used in mxTextTools:

http://www.egenix.com/products/python/mxBase/mxTextTools/

to create high performance text parsing and manipulation
tools.

> I'm getting the impression that the payoff is not worth the complexity.

-- 
Marc-Andre Lemburg
eGenix.com

Professional Python Services directly from the Source  (#1, May 08 2015)
>>> Python Projects, Coaching and Consulting ...  http://www.egenix.com/
>>> mxODBC Plone/Zope Database Adapter ...       http://zope.egenix.com/
>>> mxODBC, mxDateTime, mxTextTools ...        http://python.egenix.com/
________________________________________________________________________

::::: Try our mxODBC.Connect Python Database Interface for free ! ::::::

   eGenix.com Software, Skills and Services GmbH  Pastor-Loeh-Str.48
    D-40764 Langenfeld, Germany. CEO Dipl.-Math. Marc-Andre Lemburg
           Registered at Amtsgericht Duesseldorf: HRB 46611
               http://www.egenix.com/company/contact/