Short introduction to Python.NET at the .NET User Group in Paderborn. Displays history programming constructs and architecture.

1. INTRODUCTION TO
PYTHON.NET

2. ABOUT ME
• Stefan Schukat
• Software Architect, Physicist
• Different programming stages over the last 30 years
• Pascal, TCL/TK
• C/C++, ATL/MFC, COM, (VB)
• Python
• M
• C#
• Interest in software forensic and cross language techniques
• Twitter @tschodila
• https://www.xing.com/profile/Stefan_Schukat2

3. WHY CONSIDER PYTHON?

4. BASE OF PYTHON
• High level interpreted language
• Dynamic execution with no static typing
• Only few basic data types and programming elements are
defined
• Interpreter engine could be implemented on different
languages
• Extendable and embeddable

5. BASE PYTHON EXECUTION ARCHITECTURE
Python Code
Byte Code
Python API
Parse
Interpreter
Use
Extension
modul
Call
Native API
Call Call
C : C-Python
C# : IronPython
Java : Jython
Python : PyPy

6. PYTHON .NET
• Python Extension module for C-Python
• Access .NET runtime and libraries from Python scripting
• Combines history and amount of extensions from C-Python
with .NET
• Allows scripting access to .NET libraries in C-Python
• Allows embedding in console .NET Application to use C-Python
in .NET
• https://github.com/pythonnet/pythonnet

7. PYTHON.NET HISTORY
• Developer Brian Lloyd, Barton Cline, Christian Heimes
• Goal integrate .NET seamlessly in Python on Mono and Windows
• 1.0 for .NET 1.0 (2005), .NET 2.0 (2006)
• 2.0 Beta .NET 4.0 (2013) project abandoned
• Revived 2014 on GitHub
• Denis Akhiyarov, David Anthoff, Tony Roberts, Victor Uriarte
• 2.1 for .NET 4.x, Python 2.x, 3.x (2016)
• 2.2 for .NET 4.x, Added Python 3.6 (2017)
• .NET Core support is planned

8. PYTHON.NET ARCHITECTURE
clr.pyd
.NET
Assembly
Dynam
ic Load
PyInit_Clr
Python.Runtime.
dll
.NET Assembly
C-Export
for Python
Dll Import Python C-API
Wrapper Objects for Python Type APIs
Import Hook
Type Conversions
Reflection
…

9. PYTHON.NET RUNTIME OVERVIEW
DllImport("python.dll",
…)
DllImport("python.dll",
…)
…
Runtime
InitExt(…)
Engine PySequence
PyDict
ModuleObject
ClassObject
PropertyObject
…
Class Wrapper
for .NET Types
P-Invoke
Wrapper for C-
API
Class Wrapper
for Python
Types
…
Main entry point
Entry from Python Translation Python/NET Access Python-API

10. PYTHON .NET BASICS
• Uses reflection to initialize Python wrappers from .NET objects
• All public and protected members are available
• In case of name clash static method are preferred over instance methods
• Maps .NET namespaces to Python modules via Python import
hook
• Import statement prefers Python modules over .NET modules
• All variables in Python are reference types
• Any value type is always boxed in Python.NET
• Default mapping of data types between Python and BCL

11. TYPES MAPPING
.NET Type Python Type
String, Char unicode
Int16, UInt16, Int32, UInt32, Byte, SByte int
Int64, UInt64, UInt32 long (Py 2.x), int (Py 3.x)
Boolean bool
Single, Double float
IEnumerable list (sequence protocol)
null None
Decimal object
Struct decimal

12. ACCESSING NAMESPACE / ASSEMBLIES
>>> import clr # Initialize Runtime
>>> from System import String # Import Class from namespace
>>> from System.Collections import * # Import all from subnamespace
>>> clr.AddReference("System.Windows.Forms") # Add assembly
<System.Reflection.RuntimeAssembly object at 0x0000020A5FF06CF8>
>>> import System.Windows.Forms
>>> clr.AddReference("customsigned, Version=1.5.0.0, Culture=neutral,
PublicKeyToken=12345678babeaffe")
• Search order
• Standard Python modules
• Loaded Assemblies
• Python path for .NET assemblies (Assembly.LoadFrom)
• .NET Loader (Assembly.Load)

13. STRUCTS, METHODS, PROPERTIES
>>> import System.Drawing import Point # Import struct
>>> p = Point(5, 5) # Instantiate struct
>>> p.X # Access property
5
>>> from System import Math # Import static class
>>> Math.Abs(-212) # Access Method
212

14. GENERICS AND OVERLOADS
>>> from System import String, Char, Int32 # Import used types
>>> s = String.Overloads[Char, Int32]("A", 10) # Use overloaded constructor
>>> s # display class
<System.String object at 0x0000020A5FF64908>
>>> print(s) # Use ToString method
AAAAAAAA
>>> from System.Collections.Generic import Dictionary # Import used types
>>> d = Dictionary[String, String]() # Use generic constructor
>>> d2 = Dictionary[str, str]() # Use auto mapped types
>>> print(d) # Use ToString method
System.Collections.Generic.Dictionary`2[System.String,System.String]

15. INDEXERS, ARRAYS
>>> from System.Collections.Generic import Dictionary as d
>>> jagged = d[str, d[str, int]]() # Create dict of dicts
>>> jagged["a"] = d[str, int]()
>>> jagged["a"]["b"] = 10
>>> jagged["a"]["b"]
10
>>> from System import Array
>>> a = Array[int]([2,2])
>>> a
<System.Int32[] object at 0x0000020A5FF838D0>
>>> a[0] # Multidimensional a[1,1]
2

16. DELEGATES AND EVENTS
>>> from System import AssemblyLoadEventHandler, AppDomain
>>> def LoadHandler(source, args):
... print("Python called for {0}".format(args.LoadAssembly.FullName))
...
>>> e = AssemblyLoadEventHandler(LoadHandler) # Create delegate
>>> AppDomain.CurrentDomain.AssemblyLoad += e # Register delegate
>>> clr.AddReference("System.Windows.Forms") # Add assembly
Python called for Accessibility, Version=4.0.0.0, Culture=neutral,
PublicKeyToken=b03f5f7f11d50a3a
Python called for System.Windows.Forms, Version=4.0.0.0, Culture=neutral,
PublicKeyToken=b77a5c561934e089
Python called for System.Drawing, Version=4.0.0.0, Culture=neutral,
PublicKeyToken=b03f5f7f11d50a3a
>>> AppDomain.CurrentDomain.AssemblyLoad -= e # Unregister delegate

17. EXCEPTIONS
>>> from System import NullReferenceException # Use BCL exception
>>> try:
... raise NullReferenceException("Empty test")
... except NullReferenceException as e:
... print(e.Message)
... print(e.Source)
Empty test
None

18. COLLECTIONS
>>> from System import AppDomain # Use class which supports IEnumerable
>>> for item in AppDomain.CurrentDomain.GetAssemblies():
... print(item.FullName)
...
mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089
clrmodule, Version=2.3.0.0, Culture=neutral, PublicKeyToken=null
Python.Runtime, Version=2.4.0.0, Culture=neutral, PublicKeyToken=null
System.Core, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089
System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089
__CodeGenerator_Assembly, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null
e__NativeCall_Assembly, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null
System.Security, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a
…

19. UI PYTHON .NET
• Simple way
• Write .NET Class Assembly with UI (Winforms or WPF)
• Export functions to be used
• Hard way
• Rewrite generated code via Python.NET

20. UI WINFORMS C# CODE
using System;
using System.Windows.Forms;
namespace UILibrary
{
public partial class MainForm : Form
{
public Action PythonCallBack { get; set; }
public MainForm()
{
InitializeComponent();
}
private void ButtonCallPython_Click(object sender, System.EventArgs e)
=> this.PythonCallBack?.Invoke();
}
}

21. UI WINFORMS PYTHON CODE IN UI
APPLICATIONimport clr
clr.AddReference("UILibrary")
import UILibrary
from System import Action
def CallBack():
"""Button click event handler"""
print("Button clicked!")
MainForm = UILibrary.MainForm()
MainForm.PythonCallBack = Action(CallBack)
MainForm.ShowDialog()

22. UI WINFORMS PYTHON CODE IN CONSOLE
APPimport clr
clr.AddReference("System.Windows.Forms")
clr.AddReference("UILibrary")
import System.Windows.Forms as WinForms
import UILibrary
from System import Action
class WinFormsTest:
def __init__(self):
self.MainForm = UILibrary.MainForm()
self.MainForm.PythonCallBack = Action(self.CallBack)
app = WinForms.Application
app.Run(self.MainForm)
def CallBack(self):
"""Button click event handler"""
print("Button clicked!")
if __name__ == '__main__':
ui = WinFormsTest()

23. WINFORMS PURE PYTHON
self.buttonCallPython.Click +=
System.EventHandler(self.ButtonCallPython_Click)
self.AutoScaleDimensions =
System.Drawing.SizeF(6.0, 13.0)
self.AutoScaleMode =
System.Windows.Forms.AutoScaleMode.Font
self.ClientSize = System.Drawing.Size(245, 44)
self.Controls.Add(self.buttonCallPython)
self.MaximizeBox = False
self.MinimizeBox = False
self.Name = "MainForm"
self.Text = "TestWinforms"
self.ResumeLayout(False)
if __name__ == "__main__":
m = MainForm()
m.ShowDialog()
import clr
import System
import System.Windows.Forms
import System.Drawing
class MainForm(System.Windows.Forms.Form):
def __init__(self):
self.InitializeComponent()
def ButtonCallPython_Click(self, source, args):
print("Button clicked")
def InitializeComponent(self):
self.buttonCallPython =
System.Windows.Forms.Button()
self.SuspendLayout()
self.buttonCallPython.Location =
System.Drawing.Point(12, 12)
self.buttonCallPython.Name = "buttonCallPython"
self.buttonCallPython.Size =
System.Drawing.Size(75, 23)
self.buttonCallPython.TabIndex = 0
self.buttonCallPython.Text = "Call Python"
self.buttonCallPython.UseVisualStyleBackColor =
True

24. FURTHER USE CASES
• Automatic conversion of Python dictionary as .NET dictionary
• Usage of .NET enums as Python enums
• Routing of win32com.client COM objects as __ComObject

25. THANK YOU!
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