Python Inside .NET

Running Python Inside .NET 9 — A Complete Guide Using Python.NET

Integrating Python with .NET unlocks a powerful hybrid environment where you can leverage Python’s rich ecosystem (AI, ML, data processing) directly inside a .NET application.
In this guide, you'll learn how to run Python code, import Python modules, and call Python functions inside a .NET 9 application using Python.NET — with full source code.

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Why Use Python Inside .NET?

• Reuse existing Python scripts or ML models
• Access libraries such as NumPy, Pandas, Scikit-learn, etc.
• Extend .NET applications with data science capabilities
• No need for IPC or microservices — run Python inline

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Prerequisites

Before starting:

1. Install Python

Python 3.10 or 3.11 recommended.

2. Install dependencies

pip install numpy

3. Create a .NET 9 Console Project

dotnet new console -n PyNetIntegration
cd PyNetIntegration

4. Install Python.NET package

dotnet add package Python.Runtime

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How Python.NET Works

Python.NET embeds the CPython runtime directly inside your .NET application.

This means:

• You can call Python code from C#
• Import Python modules (even third-party)
• Exchange objects between .NET ↔ Python
• Run Python functions line-by-line or execute entire scripts

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Example 1: Run Python Inline Code

Program.cs

using Python.Runtime;

class Program
{
    static void Main()
    {
        PythonEngine.Initialize();

        using (Py.GIL())
        {
            dynamic math = Py.Import("math");
            double result = math.sqrt(144);

            Console.WriteLine($"Python sqrt(144) = {result}");
        }

        PythonEngine.Shutdown();
    }
}

✔ Works instantly
✔ No Python files needed
✔ Calls CPython directly

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Example 2: Import a Python Module (Custom .py File)

Create file: /scripts/utils.py

def add(a, b):
    return a + b

def multiply(a, b):
    return a * b

Updated Program.cs

using Python.Runtime;

class Program
{
    static void Main()
    {
        PythonEngine.Initialize();
        using (Py.GIL())
        {
            dynamic sys = Py.Import("sys");
            sys.path.append("scripts");

            dynamic utils = Py.Import("utils");
            Console.WriteLine(utils.add(10, 20));
            Console.WriteLine(utils.multiply(5, 4));
        }
        PythonEngine.Shutdown();
    }
}

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Example 3: Using NumPy Inside .NET

using Python.Runtime;

class Program
{
    static void Main()
    {
        PythonEngine.Initialize();

        using (Py.GIL())
        {
            dynamic np = Py.Import("numpy");
            dynamic arr = np.array(new int[] { 1, 2, 3, 4 });
            dynamic squared = np.square(arr);

            Console.WriteLine(squared);
        }

        PythonEngine.Shutdown();
    }
}

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Data Exchange: Python ↔ .NET

Passing .NET data to Python

var list = new List<int> { 1, 2, 3 };
dynamic npList = new PyList(list.Select(i => new PyInt(i)).ToArray());

Returning Python values to .NET

int x = (int)pyValue.As<int>();

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Folder Structure (recommended)

PyNetIntegration/
│── Program.cs
│── PyNetIntegration.csproj
└── scripts/
    └── utils.py

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When Should You Use Python.NET?

Use Python.NET when:

✓ You want to call Python inline
✓ You need NumPy/Pandas in your .NET app
✓ You need maximum speed (direct CPython runtime)

Avoid Python.NET when:

✗ You want full cross-platform runtime isolation
✗ You need Python and .NET to run separately → Use gRPC
✗ You're deploying to serverless (Azure Functions, AWS Lambda)

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Full Source Code (Copy-paste ready)

Here is the full minimal project:

PyNetIntegration.csproj

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net9.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Python.Runtime" Version="3.0.1" />
  </ItemGroup>
</Project>

Program.cs

using Python.Runtime;

class Program
{
    static void Main()
    {
        PythonEngine.Initialize();
        using (Py.GIL())
        {
            dynamic math = Py.Import("math");
            Console.WriteLine(math.sqrt(169));
        }
        PythonEngine.Shutdown();
    }
}

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Conclusion

Python.NET provides a powerful and direct way to run Python inside .NET applications.
With just a few lines of code, you can:

• Embed Python
• Run scripts
• Load modules
• Exchange data
• Use scientific libraries

This hybrid approach is perfect for AI, ML, automation, financial analysis, or any system where both ecosystems shine together.

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