Swift framework to interact with Python.

What's New

PythonKit v0.3.1



Swift framework to interact with Python.


Some Python code like this:

import sys

print(f"Python {sys.version_info.major}.{sys.version_info.minor}")
print(f"Python Version: {sys.version}")
print(f"Python Encoding: {sys.getdefaultencoding().upper()}")

Can be implemented in Swift through PythonKit with the following 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())")

Swift Package Manager

Add the following dependency to your Package.swift manifest:

.package(url: "", .branch("master")),

Environment Variables

As the Python library are loaded at runtime by PythonKit, it will try to find the most modern Python version available in the system. You can force a given version with the PYTHON_VERSION environment variable or an specific Python library path or name with PYTHON_LIBRARY.

$ PYTHON_VERSION=3 swift run
[*] Python 3.5
$ PYTHON_VERSION=2.7 swift run
[*] Python 2.7
$ swift run
[*] Python 3.5
$ PYTHON_LIBRARY=/usr/lib/x86_64-linux-gnu/ swift run
[*] Python 2.7

If PythonKit cannot find and load the Python library you can set the PYTHON_LOADER_LOGGING environment variable to know from which locations PythonKit is trying to load the library:

Loading symbol 'Py_Initialize' from the Python library...
Trying to load library at 'Python.framework/Versions/3.8/Python'...
Trying to load library at '/usr/local/Frameworks/Python.framework/Versions/3.8/Python'...
Fatal error: Python library not found. Set the PYTHON_LIBRARY environment variable with the path to a Python library.


  • If your are targeting the Mac platform with the Hardened Runtime enabled make sure you are properly signing and embedding the Python framework you are trying to load with PythonKit. The Hardened Runtime Library Validation mechanism prevents a process from loading libraries that are not signed by Apple or the same developer as the main process.


  • Originally PythonKit was based on the Python module from the Swift for TensorFlow experimental project.
  • If you have questions about PythonKit you can ask on the Swift Forums.


  • Swift Tools 5.1.0
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Last updated: Mon Nov 28 2022 09:42:28 GMT-0500 (GMT-05:00)