Getting Started with PythonKit¶

PythonKit allows calling Python code from Swift.

That sounds pretty amazing. Let’s give it a go.

Repo: https://github.com/pvieito/PythonKit

Note

You need to set Enable Hardened Runtime to No in your Xcode project to get PythonKit to work properly.

I’ve talked about Fighting with macOS’s System Integrity Protection before if you want the details, but macOS is quite particular about library paths otherwise, and you’ll likely end up with the system copy of Python 2.7!

Let’s set up a little Python that we want to call from Swift:

# In ~/Desktop/greeting.py
def hello(name):
  return f"Hello, {name}! (From Python 💃)"

Then we set a PYTHON_LIBRARY environment variable, with the path to our Python install. (I’m sure the macOS system Python is all very well and good…)

Now in Swift we can, quite miraculously I think, just import it and call our Python code:

import PythonKit

let sys = Python.import("sys")
print("Python \(sys.version_info.major).\(sys.version_info.minor)")
print("Python Version: \(sys.version)")
print("Python Encoding: \(sys.getdefaultencoding().upper())")

let dirPath = "/Users/carlton/Desktop"

func callPython() {
    sys.path.append(dirPath)
    let greeting = Python.import("greeting")
    let message = greeting.hello("Carlton")
    print(message)
}

callPython()

Here we import the Python sys module and print some basic info, before setting sys.path, importing our code and calling that.

Output will be this:

Python 3.8
Python Version: 3.8.7 (default, Jan 26 2021, 11:56:32)
[Clang 12.0.0 (clang-1200.0.32.28)]
Python Encoding: UTF-8
Hello, Carlton! (From Python 💃)

There’s so much goodness to be had in this.