How do you call PyObjC code from Objective-C?

Question

I'm a long-time Python programmer and short-time Cocoa programmer. I'm just getting started with PyObjC and it's really amazing how easy it it is to get stuff done. That said, I wanted to try using pure ObjC for my controller with PyObjC models. I might be enjoy letting Python be Python and Objective-C be Objective-C. I figured it was worth a try, anyways.

Except I can't figure out or find anything about how to call Python from Objective-C, only the other way around. Can someone point me to any resources on this? (Maybe it's on the PyObjC site but I just don't know what I'm looking for?)

Edit: I'm most interested, at the basic level, in being able to call a Python module and get some native ObjC data types back.

Answer 1

Whoops, guess I should've searched a bit more:

http://stackoverflow.com/questions/1308079/calling-python-from-objective-c

Answer 2

There are several possible approaches. The most tempting is to use py2app to compile a loadable bundle from your python code from which you can access the principal class using NSBundle. Unfortunately, this use case hasn't gotten much love from the py2app developers, and I've found several bugs in 10.5 and 10.6, including a rather nasty memory leak when passing data from python back in to Objective-C. I wouldn't recommend using py2app at thist point.

The second approach is invert the embedding. Write a Python cocoa app and load your Objective-C code from a bundle at startup (even in main()). If you already have a large Objective-C app, this may take a bit of work. The only downside, that I'm ware of, is that you won't be able to use GC in your Objective-C code, but this is really a universal limitation in working with PyObjC.

Finally, you can instantiate a python interpreter in your Objective-C code to load your python code. This is obviously more involved, but may the best option if you already have a large Objective-C codebase into which you want to inject your python code. The main.m file from the Python-Cococa application template in Xcode is a good place to start to see this in action.