How to access custom swift or objective c framework from python

The primary use case of PyObjC is to access Objective-C code from Python, but it is possible to use PyObjC to implement some functionality for an ObjC/Swift application in Python.

This is barely documented at best though. There are two ways forward for this:

1. Implement support for plugin bundles and create a plugin bundle with the python code (using py2app to package). This is documented in a very old PyObjC tutorial: https://pyobjc.readthedocs.io/en/latest/tutorials/embedded.html

2. Add explicit support for a Python extension to the application.

I'd go for the second option because that is in the end the easier option to implement.

To get there you need to do a number of things:

1. Initialise the python interpreter and run some startup code. See "Py_Initialize()" and "PyRun_SimpleString()" to get going on this (or a tutorial on embedding Python in an application).

   Make sure to release the GIL after running the startup code (this is not necessary in general when embedding, but is needed when using PyObjC and especially when different threads may call Python code)

2. Expose the ObjC API to Python

   This can be easy or hard, depending on how complicated the interface between the two parts is. Exposing ObjC classes to Python is easy: just use "objc.lookUpClass(classname)" to access an ObjC class in Python. This automatically exposes any methods on the class as well.

   Method access might require some more work, in particular when the method has pass-by-reference arguments or uses blocks.

   Accessing global variables and C functions is possible, but also requires more work because PyObjC cannot read those from the ObjC runtime API. The PyObjC documentation contains information on how to access those if you need these.

3. Set up links between the Python and ObjC parts of your code. I'd create the Python objects in Python and then add ObjC APIs (using PyObjC) to pass those to the ObjC code for the application.

   To get a nicer experience on the ObjC side you need to define protocols in ObjC that will be implemented by the Python code.

And a closing note: All of this is for accessing Objective-C APIs from Python, not Swift. This should also work with Swift code, but only if you implement ObjC interfaces in swift (@objc). PyObjC cannot be used to access arbitrary swift APIs.