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Re: Let's make a plan for python3.0 in Fedora 10+



Tim Lauridsen wrote:
Matej Cepl wrote:
On 2008-06-12, 09:16 GMT, Tim Lauridsen wrote:
also see the potential upgrade nightmare a switch to a non backwards compatibility version of python and for anaconda

Am I totally wrong when I think that 2.6 should be 100% backward compatible with 2.5 (unless explicitly requested in the python script itself and even then it should just emit DepreceatedWarnings)?

Matěj


Python will contain some forward 3.0 compability, i have not read any thing about 100% backwards compatibility.

http://www.python.org/dev/peps/pep-3000/

but even if it is, then you will have to do a

a python 2.5 to python 2.6 with (__future__) features to use some of the new stuff. and later you have to do a 2.6 with (__future__) features to python 3.0, because as they state in then pep-3000

<snip>
There is no requirement that Python 2.6 code will run unmodified on
Python 3.0
</snip>

Quoting myself:

* 2.6 appears to be mostly compatible with 2.5.x. Porting from 2.5.x to 2.6.x seems like it will be pretty routine stuff.

* 2.6 seems to be mostly compatible with 3.0 if you use from __future__ import all-the-stuff-that-changed.

* It appears that we can mix these with file-level granularity. If this works out we should be able to port individual modules to 3.0 syntax while other modules stay on 2.x.

So there will be issues that require porting between 2.5 <=> 2.6 and 2.6 <=> 3.0. But it seems like most constructs of either python2 or python3 will work on python 2.6.

Here's a project that explores the incompatibilities between 2.6 and 3.0 (although the author hasn't looked at both forward and backwards compatibility so he's a little over optimistic.

http://code.google.com/p/python-incompatibility/

For a summary of what he's found read:
  http://python-incompatibility.googlecode.com/svn/trunk/README.txt

-Toshio

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