[Python-3000] Making more effective use of slice objects in Py3k (original) (raw)

Josiah Carlson jcarlson at uci.edu
Sat Aug 26 19:00:41 CEST 2006

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.

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