[Python-3000] [Python-ideas] Namespaces are one honking great idea -- let's do more of those!

[Andrew McNabb]

I really like your point about how Python should give a better error
than a SyntaxError when a Python 2 script is run on a Python 3
interpreter.  I agree that the cause of problems should be pointed out
clearly to end users.  However, I disagree that adding a new file
extension is necessary.

On Mon, Feb 04, 2008 at 03:34:56PM -0800, Ralf W. Grosse-Kunstleve wrote:
> 
> If the success of Python is to continue, you have to give your large
> user base a clear path to working with two co-existing Python
> versions, so that installing a Python 3 application doesn't break all
> Python 2 applications (some of which may never be converted since the
> original developers have moved on). For example, I really need to be
> able to use wxPython based on Python 2 and wxPython based on Python 3
> simultaneously on my Windows machine. I'm thinking this is only
> possible if Python 3 uses a new file extension.

In Python 2, "import wxPython" will import wxPython based on Python 2,
and on Python 3, it will import wxPython based on Python 3.  There
wouldn't be a Python 2 version of wxPython in the python3.0
site-packages.


> Ideally, I'd even want to have both Python 2 and Python 3 scripts in
> the same directory, while incrementally converting our applications.
> I'd want to cp script.py script.py3, then edit the .py3 version until
> it works, while still being able to run the old version during the
> migration period.

I kind of like the idea of doing the following:

import sys
major_version = sys.version_info[0]
if major_version == 2:
    import script2
    script2.main()
elif major_version == 3:
    import script3
    script3.main()

It really shouldn't be too bad, I think.


-- 
Andrew McNabb
http://www.mcnabbs.org/andrew/
PGP Fingerprint: 8A17 B57C 6879 1863 DE55  8012 AB4D 6098 8826 6868
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