[Python-Dev] Alternative to more ABCs [was:] Iterable String Redux (aka String ABC) (original) (raw)

Guido van Rossum guido at python.org
Mon Jun 2 00:57:09 CEST 2008

On Sun, Jun 1, 2008 at 6:57 AM, Paul Moore <p.f.moore at gmail.com> wrote:

2008/6/1 Guido van Rossum <guido at python.org>:

The case for String has already been made.

Actually I'm not sure. One you know that isinstance(x, String) is true, what can you assume you can do with x? [...] Right. I'm now beginning to wonder what exactly you're after here -- saying that something is an "X" without saying anything about an API isn't very useful. You need to have at least some API to be able to do anything with that knowledge. Apologies to Raymond if I'm putting words into his mouth, but I think it's more about not doing things with the type - a String is a Sequence that we don't wish to iterate through (in the flatten case), so the code winds up looking like for elem in seq: if isinstance(elem, Sequence) and not isinstance(elem, String): recurse into the element else: deal with the element as atomic

I thought that was he meant too, until he said he rejected my offhand suggestion of Atomic with these words: "Earlier in the thread it was made clear that that atomicity is not an intrinsic property of a type; instead it varies across applications [...]"

This implies that other "empty" abstract types aren't useful, though, as they are not subclasses of anything else...

There's a thread on this out now I believe.

-- --Guido van Rossum (home page: http://www.python.org/~guido/)

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