[Python-3000] Warning for 2.6 and greater

[Anthony Baxter]

On Monday 08 January 2007 16:50, Anthony Baxter wrote:
> I've been thinking a little about how and where we'd add warnings
> to 2.6 and later for things that will break in 3.0. My first idea
> is to add a command line option '-3' (or maybe '-warn3')
> implemented as "from __future__ import py3k". We can then put
> code in that optionally generates a warning if this is set.

Ok, I lied - I implemented this pretty easily just now (patch 
attached). As a first pass, I put in warnings for dict.has_key and 
the builtin apply() function. 

I've changed my mind about the from future statement. I think that
'from __future__ import py3k' says "please use whatever backwards 
incompatible 3.x features that you support". I guess we could have 
something like 'from __future__ import warn3k', perhaps. But this 
wouldn't take effect for just the current source file, so could be 
confusing. 

If people are happy with this, I'll check it into the trunk, then 
people can go crazy adding other warnings for 3.0-isms. 

beaker% ./python
Python 2.6a0 (trunk:53285:53286M, Jan  8 2007, 18:34:47) 
[GCC 4.1.2 20060928 (prerelease) (Ubuntu 4.1.1-13ubuntu5)] on linux2
Type "help", "copyright", "credits" or "license" for more 
information.
>>> 1 in {}
False
>>> {}.has_key(1)
False
>>> apply(lambda x:None, (1,))
>>> 
beaker% ./python -3 
Python 2.6a0 (trunk:53285:53286M, Jan  8 2007, 18:34:47) 
[GCC 4.1.2 20060928 (prerelease) (Ubuntu 4.1.1-13ubuntu5)] on linux2
Type "help", "copyright", "credits" or "license" for more 
information.
>>> 1 in {}
False
>>> {}.has_key(1)
__main__:1: DeprecationWarning: dict.has_key not supported in 3.x
False
>>> apply(lambda x:None, (1,))
__main__:1: DeprecationWarning: apply() not supported in 3.x
>>> 

Anthony
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