[Python-ideas] improve compatibility

[Liam Marsh]

oops..
I sent an answer to  andrew barnert, who have sent the first answer to my
question, and not to the list...
however , I do have an answer to my question.
thank you!

2014-11-29 11:51 GMT+01:00 Andrew Barnert <abarnert at yahoo.com>:

> On Nov 29, 2014, at 0:46, Liam Marsh <liam.marsh.home at gmail.com> wrote:
>
> hello,
>
> yes, the bug which gave me this idea is a py3.2 to py3.3 bug with Vpython,
> a 3D graphs library.
>
>
> And is the bug a stdlib bug, or a language bug?
>
> I also thought this will be the reconciliation between py2 and py3. (this
> is why I thought the packs will include a version of the stdlibs)
>
>
> The language differences between 2.x and 3.x are huge, and most of the
> stdlib differences between 2.6 and 3.1 or 2.7 and 3.2 are related to those
> language differences. Porting code to 3.x is primarily about fixing Unicode
> stuff, or code that was already deprecated in 2.5 or 2.6 but wasn't broken
> until 3.x. Having the 2.7 stdlib in 3.x would be a huge amount of work for
> almost no benefit.
>
> in fact, how do the .pyc work? were them modified by the "language and
> implementation changes"? how do them import other modules?
>
>
> .pyc files are just compiled bytecode, with a version-specific header.
> If you fixed the 2.7 stdlib to work in 3.x (which, again, would be a huge
> amount of work), you could compile it with 3.4.
>
> But you're missing the fact that large chunks of the stdlib are written in
> C, and compiler against the Python C API. And parts of the stdlib
> (especially builtins and the sys module) are exposing types and functions
> written in C that are part of the core implementation, so the 2.x version
> of the sys module wouldn't be compatible with 2.x code anyway.
>
> Also, did you mean to write just to me instead of to the list?
>
>
> thank you!
>
>
>
> 2014-11-29 6:07 GMT+01:00 Andrew Barnert <abarnert at yahoo.com>:
>
>> On Nov 28, 2014, at 8:29, Liam Marsh <liam.marsh.home at gmail.com> wrote:
>>
>> > hello,
>> > the problem is that even with extreme precaution, it is impossible to
>> keep ALL modules compatible from a version to another.
>>
>> Do you have a specific library or app that you've had a problem with?
>> There were a handful of modules that had a problem with the 3.2 to 3.3
>> conversion, but every one I saw was caused by language and implementation
>> changes, not stdlib changes. I don't think I've seen anything that works
>> with 3.3 but not 3.4. I'm sure it's not impossible for such a thing to
>> happen, but it would be helpful to have at least one real-life example.
>>
>> > what I want to ask is this:
>> > -some "packs" which can, like py-compile, generate .pyc files, but
>> using "old" versions of the default library, and of __builtins__.
>>
>> But how would this work? The same changes that broke a handful of
>> third-party modules between 3.2 and 3.3 probably also mean that the 3.2
>> stdlib wouldn't work in 3.3 without minor changes. And as for builtins,
>> most of those are exposing internals of the implementation, so trying to
>> make the 3.2 builtins work with 3.3 would take a lot more work than just
>> building the 3.2 code against 3.3.
>>
>> > -One will go with every minor version and will be optionnal in the
>> installation
>> > -any imported py file will be able to choose which version it wants
>> with the
>> >    "#! py recommended version X.X" or
>> >    "#! py mandatory version X.X" commentaries at the begining of the
>> file.
>> >
>> > thank you and have a nice day/evening/night.
>> > _______________________________________________
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>
>
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