IronPython is an implementation of Python based on Python.Net.

Installation

Installing IronPython

Download IronPython.3.4.0-alpha1.zip
Extract the folder to your Unity project in Assets/Plugins. You should now have Assets/Plugins/IronPython.3.4.0-alpha1 in your Unity Project.
Download Microsoft.Scripting.Metadata.dll and Microsoft.Scripting.Metadata.xml
Move these two files into Assets/Plugins/IronPython.3.4.0-alpha1/net46.
In Assets/Plugins/IronPython.3.4.0-alpha1, delete these folders:
- net5.0
- net5.0-windows
- netcoreapp2.1
- netcoreapp3.1
- netstandard2.0
When everything is compiled you might see an error with IronPython.Wpf.dll.
- In the Assets/Plugins/IronPython.3.4.0-alpha1/net46/DLLs folder, delete IronPython.Wpf.dll. It seems to be unnecessary and fixes the issue.
You also should go to Edit > Project Settings > Player > Other Settings > Configuration and change the Api Compatibility Level to .Net 4.x to be safe. Apparently there can be some issues using .Net Standard 2.0.

Since IronPython is based on .NET and not C like CPython, you cannot use libraries which are C based. Numpy is the big one that comes to mind.

In command prompt, cd into the /IronPython.3.4.0-alpha1/net46 directory.
Execute ipy -X:Frames -m ensurepip, which makes sure you have pip installed.
Now you can add any library you want by executing ipy -X:Frames -m pip install library-name.
** This seems to correctly install the libraries, however I'm still getting errors when importing libraries into Python scripts. The errors seem unrelated though, they have to do with the Microsoft.Scripting.Interpreter.

Using the IronPython.Hosting namespace and the Microsoft.Scripting.Hosting namespace
Create the engine
- ScriptEngine engine = Python.CreateEngine();
Add the location of any libraries you want to use to the engine's search paths.
- ICollection<string> searchPaths = engine.GetSearchPaths();
  searchPaths.Add(@"C:/Location_of_Unity_project/Assets/Plugins/IronPython.3.4.0-alpha1/Lib");
  searchPaths.Add(@"C:/Location_of_Unity_project/Assets/Plugins/IronPython.3.4.0-alpha1/Lib/site-packages");
  engine.SetSearchPaths(searchPaths);
Use the engine to run a Python script
- dynamic py = engine.ExecuteFile("C:/path/to/file.py");
Use py to access variables, methods, classes, etc in the Python script using dot notation
- See script.py and CallingPython.cs for examples of how to do this.
If you simply want to run the script and don't care about accessing any data, you can skip assigning the variable
- engine.ExecuteFile("path/to/file.py");