> Embedding Python 2 inside of Python 3 (or vice-versa) is not very hard to do on Linux. Simply `dlmopen` the .so in a new linker namespace and write a little bit of bridging code to interface the two object layouts.
Where can I pip install this from?
Or is there a reason that none of the huge numbers of python users delaying their transition as much as possible until all their libraries were updated built it?
The above will launch ("embed") a Python 2 or Python 1.5 interpreter from within a Python 3 interpreter. If you use `dlmopen` and `LM_ID_NEWLM`, the guest interpreter will have its own linker namespace. In other words, the guest interpreter (and any DSOs it opens) will be totally isolated from the host interpreter.
The above shows the use of `PyRun_SimpleString`. Since `PyRun_String` accepts a `PyObject* globals` and `PyObject* locals`, you could build a very basic bridge in <30 lines of code by using serialisation to copy and convert. (For user-defined classes, you would need something better.)
I've given a many talks about this at various Python and PyData conferences. (I've mentioned it a number of times on HN, both in response to complaints about the Python 2→3 transition and in response to comments like yours suggesting this solution to that problem.)
Though presented as a joke, the approach could be made to work with some effort. I can't speculate on why no one has ever followed-up on it, and I can't speculate on why the Python 2→3 transition has been so difficult for some users. Perhaps in some places, financial or organisational arguments are more influential than technical arguments.
Where can I pip install this from?
Or is there a reason that none of the huge numbers of python users delaying their transition as much as possible until all their libraries were updated built it?