ubernostrum on Django and Python 3

I've said before and will say again:

The holdup here is not technical. It's great that we've got people like Alex willing to port code, but that's not the hard part. The hard part is people who are using and want to continue using Django on platforms where Python 2.5 or even 2.4 is still the standard.

More on this forthcoming, once I've had a proper weekend off.

glenjamin 15y

How feasible is it to have support from 2.4 to 3.x? Either with or without 3to2/2to3 as part of the packaging process?

EDIT: I'd have thought upgrading the codebase to 3.x and making sure that 3to2 produces a working 2.4 version would be better than using 2to3. Thoughts?

koenigdavidmj 15y

The problem there is that 2.4's exception statements and 3.0's have two different meanings.

2.4 only supports this:

    try:
        do stuff
    except FooError, e:
        do stuff with e

3.0 and up choke on this; they interpret it as "catch exceptions of type FooError or e and do not give the exception object a name".

2.5 through 2.7 interpret like 2.4 but also support explicit parentheses to do what Python 3 does:

    try:
        do stuff
    except (FooError, BarError) as e:
        do stuff
    except (BazError, QuxError):
        do other stuff

2to3 requires that you use the new exception syntax only, to avoid confusion.

briancurtin 15y

The following will work across 3 and 2 versions going back pretty far. It's necessary if you want to support pre-2.5 versions (where `as` was introduced):

    import sys
    try:
        fn()
    except (IOError, TypeError):
        err = sys.exc_info()[1]
        print(err)

http://docs.pythonsprints.com/python3_porting/py-porting.htm...

koenigdavidmj 15y

Still kind of ugly, and not something which you want to litter than Django sources. Especially if you are going to put them all back when 2.4 support is dropped.

kingkilr 15y

That is precisely my goal, I think it's eminently feasible using 2to3.

scorpion032 15y

I think django should include magic to fall back to 2.x version when and where 3.x is not available. May be via configuring multiple virtualenvs.

oreilly 15y

For platforms where an older version of python is standard, can that not be worked around by using virtualenv?

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