Using Python With Swift 3

(TL;DR: Create a python .plugin bundle with py2app, load it in main.swift and use @objc protocols to specify concrete interfaces for the python classes to implement. Example here.)

(This is an update to an earlier article for compatability with Swift 3 and XCode 8.1. There has been a couple of name and interface changes, but nothing major.)

I wanted to use an existing library of python code that I had written, in a new macOS application - to provide an easy-to-use UI for the library. I wanted to use Swift, both because I find it an infinitely nicer language than Objective-C, and it seems Swift is now accepted as mainstream.

There is lots of information around on how to integrate python with Objective-C via the pyobjc python library, but a lot of information is very old and I couldn’t find anything that discussed or was even as recent as Swift.

The best way to create executable bundles with python is with py2app, which has two modes of operation - creating an executable application .app bundle with the main executable written in python and calling into compiled swift code, and creating a python-based .plugin bundle that is loaded by the Swift-based application. After having various issues working with the .app method, I decided to use the .plugin approach, despite the relative lack of documentation.

This article shows a very basic application to demonstrate the fundamental principals of integrating swift and python.

Using Python With Swift

Update 2017/11/4: I’ve updated this post for compatability with Swift 3 and XCode 8.1 here.