[Python-Dev] The bytes type (original) (raw)

Phillip J. Eby pje at telecommunity.com
Tue Jan 16 19:51:27 CET 2007

At 09:50 AM 1/16/2007 -0800, Guido van Rossum wrote:

Actually it's very easy to write code using keys(), items() and values() that works as well in 2.2 as it works in 3.0: never use the iter* variants, and don't sweat the performance costs of creating a list so much. If you can't afford to create a list, iterate over the dict itself, which will give you the keys in both versions.

Actually, the main reason I use items() or keys() is because I want to mutate the dictionary, or because something else is going to mutate it while I'm looping over it. But yeah, that discussion should be on Py3K.

Without having at least some 2.x version that can run 3.x code, I think there is little chance of 3.0 becoming viable. You've been comparing this to Zope 2/Zope 3, but in that world there is something called "Five" that lets you do Zope 3 things inside of Zope 2, so you have some chance of porting your code in an incremental fashion, without having to leap everything over in one go. I'm not aware of compromises to 3.0's architecture that were made in order to ease the transition though -- all of the burden was placed on Zope 2.x (though perhaps some optional compatibility packages were also added to Zope 3.0?).

Right, which is why I don't think we should worry about 2.5 as much as 2.6.

The analogy isn't perfect, because we are not so much trying to provide backward compatibility in "Excel" as to add forward compatibility to "123", but you get the idea. Such analogies are hard to get right; in this case he's talking about file interchange formats. Perhaps the closest analogy is pickling.

Actually, I meant the analogy for code. If you can't write code that runs on some 2.x + 3.x combination, you have no way to cross the chasm. If you're writing "spreadsheets for Excel" (code that runs on 3.x), you need to be able to "share them with 1-2-3 users" (run that code on 2.x).

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