On 28.02.2014 01:48, James Powell wrote:
On 02/27/2014 06:51 PM, M.-A. Lemburg wrote:
On 28.02.2014 00:26, ian o wrote:
[... Embed Python 2 in Python 3 ...]
Thoughts or criticisms?
There's a catch here: Python 2 and Python 3 use the same C APIs, so you'd have to separate the two in some way to make both live in the same process.
I actually have a working embedding of Python 3 into Python 2, which I've presented at a few conferences, most recently at PyData London this past weekend.
It's just a C-extension module that embeds a Python 3 PyRun_SimpleString. I haven't gotten around to building a shim to interact with Python 3 objects in Python 2 (and this would require a little bit of sophistication to handle GIL, GC, &c. issues.)
Still, it's a working example of Python 2 and Python 3 running in the same process.
Interesting :-) Do you have some pointers to slides or videos ? I'm been thinking of doing something like this but the other way around - embed Python2 in Python3. When starting to brainstorm that idea, I quickly ended up postponing the idea again due to problems with C extension linking, dual interpreter environments, object interfacing between the two worlds, having two separate exception class trees, two sets of basic types/classes, two GILs, etc. The linking part was the most important to me, since being able to use Python 2 extensions would be my main reason to stick with Python 2 for some more time.
It's not impossible, but it can potentially ruin the idea, since C extensions for both Python versions will have to link the right set of C APIs.
I did this by "source filtering" - i.e., rewriting exported symbols to allow linking against both interpreters. This is admittedly a very primitive approach and limits its use in production.
I recently put some time into trying to redo this embedding using cffi and worked through a few problems in this approach with one of the cython/numba developers. I haven't gotten anything working yet. I may need to ask Xzibit if he has any suggestions.
I don't know if this idea has any serious applications. It's definitely been a fun toy for presenting ideas about interpreter embedding and exploring certain facets of CPython!
Cheers, James Powell
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