[Python-3000] Making more effective use of slice objects in Py3k

[Josiah Carlson]

Nick Coghlan <ncoghlan at iinet.net.au> wrote:
> 
> This idea is inspired by the find/rfind string discussion (particularly a 
> couple of comments from Jim and Ron), but I think the applicability may prove 
> to be wider than just string methods (e.g. I suspect it may prove useful for 
> the bytes() type as well).

A couple comments...

I don't particularly like the idea of using lists (or really iter(list) ),
range, or slice objects as defining what indices remain for a particular
string operation.  It just doesn't seem like the *right* thing to do.

> There are a couple of existing workarounds for this: buffer() objects, and the 
> start/stop arguments to a variety of string methods. Neither of these is 
> particular convenient to work with, and buffer() is slated to go away in Py3k.

Ahh, but string views offer a significantly more reasonable mechanism.

string = stringview(string)

Now, you can do things like parition(), slicing (with step=1), etc., and
all can return further string views.  Users don't need to learn a new
semantic (pass the sequence of indices).  We can toss all of the
optional start, stop arguments to all string functions, and replace them
with either of the following:
    result = stringview(string, start=None, stop=None).method(args)
    
    string = stringview(string)
    result = string[start:stop].method(args)


Perhaps one of the reasons why I prefer string views over this indices
mechanism is because I'm familliar with buffers, the idea of just having
a pointer into another structure, etc.  It just feels more natural from
my 8 years of C and 6 years of Python.


 - Josiah