Using the Python API

The Python Script Editor makes it easy to test Python scripts and to create a menu item to allow users to easily access the script.

In addition you can directly call Python from your C# scripts. Python for Unity offers a high-level API and a low-level API.

High-level API: PythonRunner.RunString

The following C# code will create a menu item that prints "hello world" in the Unity console:

using UnityEditor.Scripting.Python;
using UnityEditor;

public class HelloWorld
{
    [MenuItem("Python/Hello World")]
    static void PrintHelloWorldFromPython()
    {
        PythonRunner.RunString(@"
                import UnityEngine;
                UnityEngine.Debug.Log('hello world')
                ");
    }
}

You can use any assembly that is available in C# by simply importing it with the Python import statement -- in the example, we show importing UnityEngine.

PythonRunner.RunFile

Instead of inlining your Python code inside of a C# script, you can execute a whole Python script using the PythonRunner.RunFile method. For example, this Python script loops over all the GameObjects in a scene and makes sure all the names end up with an underscore:

import UnityEngine

all_objects = UnityEngine.Object.FindObjectsOfType(UnityEngine.GameObject)
for go in all_objects:
    if go.name[-1] != '_':
        go.name = go.name + '_'

Put this file in Assets/ensure_naming.py. Script files can be located anywhere on your file system, they don't need to be in the project. You can run this Python script from C# as follows:

using UnityEditor.Scripting.Python;
using UnityEditor;
using UnityEngine;

public class EnsureNaming
{
    [MenuItem("Python/Ensure Naming")]
    static void RunEnsureNaming()
    {
        PythonRunner.RunFile($"{Application.dataPath}/ensure_naming.py");
    }
}

Low-level API

You can directly use Python for .NET, which wraps the CPython API. Using the C# dynamic type, you can write C# that looks like Python. Refer to the Python for .NET documentation.

There are some caveats:

• Make sure Python is properly initialized by calling PythonRunner.EnsureInitialized().
• Always grab the CPython Global Interpreter Lock (GIL).

Sample code:

using Python.Runtime;
using UnityEditor.Scripting.Python;

public class MyPythonScript
{
    [MenuItem("MyPythonScript/Run")]
    public static void Run()
    {
        PythonRunner.EnsureInitialized();
        using (Py.GIL()) {
            try {
                dynamic sys = PythonEngine.ImportModule("sys");
                UnityEngine.Debug.Log($"python version: {sys.version}");
            } catch(PythonException e) {
                UnityEngine.Debug.LogException(e);
            }
        }
    }
}

You'll need to add an assembly reference in order for the compiler to know where to find the low-level API in Python.Runtime. In the project view, right-click and create a new assembly reference:

Then add a reference to com.unity.scripting.python.editor: