pythonnet - Python.NET

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Python.NET is a package that gives Python programmers nearly seamless integration with the .NET Common Language Runtime (CLR) and provides a powerful application scripting tool for .NET developers. It allows Python code to interact with the CLR, and may also be used to embed Python into a .NET application.

Calling .NET code from Python

Python.NET allows CLR namespaces to be treated essentially as Python packages.

.. code-block:: python

import clr from System import String from System.Collections import *

To load an assembly, use the AddReference function in the clr module:

.. code-block:: python

import clr clr.AddReference("System.Windows.Forms") from System.Windows.Forms import Form

By default, Mono will be used on Linux and macOS, .NET Framework on Windows. For details on the loading of different runtimes, please refer to the documentation.

.NET Core

If .NET Core is installed in a default location or the ``dotnet`` CLI tool is on
the ``PATH``, loading it instead of the default (Mono/.NET Framework) runtime
just requires setting either the environment variable
``PYTHONNET_RUNTIME=coreclr`` or calling ``pythonnet.load`` explicitly:

.. code-block:: python

   from pythonnet import load
   load("coreclr")

   import clr


Embedding Python in .NET
------------------------

-  You must set ``Runtime.PythonDLL`` property or ``PYTHONNET_PYDLL`` environment variable
   starting with version 3.0, otherwise you will receive ``BadPythonDllException``
   (internal, derived from ``MissingMethodException``) upon calling ``Initialize``.
   Typical values are ``python38.dll`` (Windows), ``libpython3.8.dylib`` (Mac),
   ``libpython3.8.so`` (most other Unix-like operating systems).
-  Then call ``PythonEngine.Initialize()``. If you plan to use Python objects from
   multiple threads, also call ``PythonEngine.BeginAllowThreads()``.
-  All calls to python should be inside a
   ``using (Py.GIL()) {/* Your code here */}`` block.
-  Import python modules using ``dynamic mod = Py.Import("mod")``, then
   you can call functions as normal, eg ``mod.func(args)``.
-  Use ``mod.func(args, Py.kw("keywordargname", keywordargvalue))`` or
   ``mod.func(args, keywordargname: keywordargvalue)`` to apply keyword
   arguments.
-  All python objects should be declared as ``dynamic`` type.
-  Mathematical operations involving python and literal/managed types
   must have the python object first, eg. ``np.pi * 2`` works,
   ``2 * np.pi`` doesn't.

Example
~~~~~~~

.. code-block:: csharp

   static void Main(string[] args)
   {
       PythonEngine.Initialize();
       using (Py.GIL())
       {
           dynamic np = Py.Import("numpy");
           Console.WriteLine(np.cos(np.pi * 2));

           dynamic sin = np.sin;
           Console.WriteLine(sin(5));

           double c = (double)(np.cos(5) + sin(5));
           Console.WriteLine(c);

           dynamic a = np.array(new List<float> { 1, 2, 3 });
           Console.WriteLine(a.dtype);

           dynamic b = np.array(new List<float> { 6, 5, 4 }, dtype: np.int32);
           Console.WriteLine(b.dtype);

           Console.WriteLine(a * b);
           Console.ReadKey();
       }
   }

Output:

.. code:: csharp

   1.0
   -0.958924274663
   -0.6752620892
   float64
   int32
   [  6.  10.  12.]



Resources
---------

Information on installation, FAQ, troubleshooting, debugging, and
projects using pythonnet can be found in the Wiki:

https://github.com/pythonnet/pythonnet/wiki

Mailing list
    https://mail.python.org/mailman/listinfo/pythondotnet
Chat
    https://gitter.im/pythonnet/pythonnet

.NET Foundation
---------------
This project is supported by the `.NET Foundation <https://dotnetfoundation.org>`_.

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