Tarn Barford

Im doing an introduction to IronPython presentation at the Victoria .NET user group tomorrow, I've been attending the user group for about a year and Im pretty excited about presenting. I think python is a fantastic language and its great to be able to build software on the .NET framework with it.

The Slides

Introduction

I wanted to start with the second slide and have a photo of a pub on the contact slide but decided to get through this before trying out PowerPoint jokes.

Why Python

I just plan to discuss Why I started using Python. The cartoon is, of course, XKCD.

Python

Basic information about the language and its background. Would have liked to have added meta programming or at least .. to the paradigms.

I think its a fantastic language so I'll mention its expressive, fun, productive or whatever adjectives I've got in my head at the time.

People using Python

I really want to demonstrate that Python is real language, being used by real people, to write real code.

I probably should also have mentioned Google App Engine here which I've been tinkering with a bit recently and think is pretty cool.

IronPython

The Python language on .NET. Most of the demo is doing cool stuff in .NET with the Python language. I think it goes further than this and allows developers to use their own paradigms and patterns to do .NET development.

C# and IronPython comparison

I saw this example in the awesome Iron Python in Action book. I included it as its a great introduction IronPython code, as it clearly and simply shows differences on similarities with C#.

Dynamic Language Runtime

The Dynamic Language Runtime project is open source. Its quite well described here as:

IronLisp has been superseded by the IronScheme project.

Dynamic Typing

This slide is just a brief overview of what duck typing is.

It is great for writing test objects, but I have a slide for the later.

Interactive Interpreter

I think its awesomely cool, and I use it through the entire demo so I thought it might be worth warning people.

The Demo

The demo is a series of scripts run into the IronPython Interactive Console. I've uploaded the very small collection of scripts for this demo here.

IronPython and the CLR

Create a string, show how its methods can be reflected. Import the CLR and show how the .NET String methods are now available.

# Introduction to IronPython and the CLR

# Standard first Python console command
2 + 2

# Create a string
s = 'Hello IronPython'

# Inspect its methods, note that its only Python methods.
dir(s)

# Python has a method to make the text uppercase
s.upper()

# Import the CLR
import clr

# Now look at the same objects methods,

# We now see the .NET string methods!
dir(s)

# And can use them!
s.ToUpper()

Screen Shot

Using a .NET Classes

Create a WebClient object from the .NET framework to download an RSS feed. Use an xml2py module written by Harry Pierson to deserialise the RSS feed into an object graph. Then send the dates and titles to the Speech Synthesizer. I've seen this done before in an IronPython presentation, and just thought it was to much fun to leave out.

import clr

# Create a WebClient and download a string of XML
from System.Net import WebClient
w = WebClient()
xml = w.DownloadString('http://feeds.theage.com.au/rssheadlines/technology.xml')

# Lets have a look at first 60 characters of the xml..
print xml[0:60]

# If bad stuff happens in the presentation..

#xml = open('theage.rss').read()

# Deserialize to objects using xml2py

from devhawk import xml2py
rss = xml2py.parseString(xml)

# Print the results
for post in rss.channel.item:
  print post.pubDate, post.title

# Import Speech
clr.AddReference('System.Speech')
from System.Speech import *
ss = Synthesis.SpeechSynthesizer()

# Say titles and dates using the SpeechSynthesizer
for post in rss.channel.item:
  s = "%s. %s." % (post.pubDate[:16], post.title)
  ss.SpeakAsync(s)

Screen Shot

SQL

I really dont want to do this in the presentation. I did spend a fair amount of time playing round with asynchronous SQL queries for use in a WPF application, but it seemed too complicated for the demo so I've left it out. I use

# import a simple wrapper around System.Data.SqlClient
# the wrapper is on my blog, I just wanted to show the AdventureWorks
# database, it seems a bit of .NET presentation tradition.

from demo import sql

# setup a query on the AdventureWords database
query = 'SELECT * FROM Production.Product'

sql.connection = 'Data Source=localhost\SQLEXPRESS;InitialCatalog=AdventureWorks;Integrated Security=SSPI;'

# execute the query
products = sql.SqlQuery(query)

# print some results
for p in products[:5]:
  print p.Name

WPF, Data Binding and Exec

I think there is some pretty cool stuff in this demo. Although it takes a lot more to write real applications it does open new ways to develop and test .NET applications.

# More pythonic way of getting the feed.. lets hope I have internet
from devhawk import xml2py
rss = xml2py.parse('http://feeds.theage.com.au/rssheadlines/technology.xml')

# Importing avalon starts a new thread to run the WPF application
# It sets up some dispatures so the console can talk to the GUI

from samples import avalon

# Create a window, show it and load some XAML into it
w = avalon.Window()
w.Show()
xaml = avalon.LoadXaml('demo.xaml')
w.Content = xaml

# Loading names is really cool, it traverses the control tree
# described in the XAML and creates a dictionary of names and
# controls. We can add those dictionary items to the local scope,
# so we get the same effect as a generated designer files in
# Visual Studio.

avalon.LoadNames(xaml,locals())

# We can bind a Python list of Python objects to the ListView
listView.ItemsSource = rss.channel.item

# Create a button click callback that will execute the script
# in the query TextBox.
def OnClick(*args):
  try:
    exec (query.Text)
  except:
    print "Script threw an exception"
  pass

# Wire up the click event to our function
execute.Click += OnClick

# We can now execute this on the client
listView.ItemsSource = [p for p in rss.channel.item if p.title.find('to')>= 0]