Python 3

[John Arbash Meinel]

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> As for the extension guidelines, 'meh'. For reference they are:
> --
...
> It is not recommended to try to write source code that runs unchanged
> under both Python 2.6 and 3.0; you’d have to use a very contorted
> coding style, e.g. avoiding print statements, metaclasses, and much
> more. If you are maintaining a library that needs to support both
> Python 2.6 and Python 3.0, the best approach is to modify step 3 above
> by editing the 2.6 version of the source code and running the 2to3
> translator again, rather than editing the 3.0 version of the source
> code.
> --

a) We actually try to avoid 'print' since we really want to be writing
to specific file output (and print >>foo is pretty ugly anyway)

b) we don't really use metaclasses. I know we use __new__ in one or two
places (revspec), but really only because we wanted to compatibly raise
an error if someone used __init__ directly.


> 
> We haven't really ignored them - we are ported to 2.6, we have
> fantastic test coverage. Folk who are doing Python 3 work can use the
> -3 switch; I'm interested here in how we enable those folk to have an
> easy life, not in the mechanics of actually doing the work - that is a
> separate, albeit related, problem.
> 2to3 is a problem for us. Here's the problem:
>  - folk will want 3 before there are no platforms that have python2.x
> and not python3.x support.
>  - 2to3 means an indeterministic program is actually run
>  - I like to be able to properly support things
>  - distros would prefer to ship a single 'bzr' package rather than two
> separate ones - and because they run with precompiled files not
> writable by the user...
> 
> python2to3 is essentially useless to us. IMNSHO. Its a great tool for
> understanding *the first pass* of what needs to be changed, but not
> for actually having a supported result.
> 
> As for the 'not recommended' clause - the *Python 3* release manager
> has submitted patches to another project - testtools - that does
> precisely that, a single source that works. And its actually pretty
> nice.
> 
> -Rob

I'll just note that PyQt has some v3 support, nad it causes some real
headaches for the Windows installer. Because the code is listed in a
conditional import (something like: if sys.? > (2, 5, ...) import py3).
It means that py2exe wants to include that code, but can't even import
it without getting an exception.

I don't know what that would mean for us, but splitting the codebase
there wasn't nice for some 3rd party tools.

John
=:->

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