[Python-Dev] [Python-3000] Warning for 2.6 and greater

[Barry Warsaw]

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On Jan 10, 2007, at 2:42 PM, Thomas Wouters wrote:

> The idea is that we only generate the warnings optionally, only for  
> things
> that can be written in a manner compatible with prevalent Python  
> versions,
> and in the most efficient manner we can manage, *except* for the  
> few things
> that are already considered (by many) criminal to use: input(),  
> backtics,
> mixed tabs and spaces. In other words, for any code written even  
> remotely
> sane in the last five years, no extra warnings will be generated.  
> By Guido's
> plan, 3.0 will arrive well before 2.6, and the migration step is  
> not as
> large as many fear it to be. Having Python 2.6 optionally warn for
> 3.0-compatibility is a lot easier for the average developer than  
> having a
> separate tool or a separately compiled Python.

I tend to agree with Raymond that Python 2.x will live longer than  
any of us think it might, or would hope for.  I think it's even  
possible that there will be enough commercial impetus to keep 2.x  
alive with security updates (though with no new features) for a long  
while after 2.9 is released.  I also think that the migration path  
may be more difficult than we think, especially with the unicode/str  
changes.  Maybe it will be smooth and easy, but we don't know yet.   
(Heck, my company probably won't even upgrade from Python 2.4 to  
Python 2.5 any time soon.)

Having said that, I don't have too much of a problem with the general  
guidelines Thomas outlines above.  Just be really careful about what  
you criminalize in 2.6 because each will cause some current users  
pain.  I think the other thing we've learned is that we may not know  
how much pain we cause until after Python 2.6.0 is released and ultra- 
conservative users start to upgrade.  I can probably get on board  
with the three specific cases you mention above, because /my/ code is  
probably safe (although I wouldn't be surprised if some 10+ y.o. code  
still has a few lurking backticks), but I might balk if that slope  
gets any more slippery.

- -Barry

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