IronPython is your friend - Part 1 - IronPython and delegates….

I felt like posting some code snippets... so I was looking around
and thought perhaps some IronPython might be interesting.... Some
of you may find this useful, possibly not.  I tend to
explore functionality using unit tests, so all my code will be
test cases - I might make this part of a small series on looking
at python code with a view to integrating it into an existing
system as a scripting engine.  Lets call the series
"IronPython is your friend"... because it really is.

Part 1 - IronPython and delegates....

So you have downloaded the IronPython runtime dll's, and you
would like to start integrating it into some project your working
on... first off lets create a python engine, and make sure it

public void GetGoing()
PythonEngine engine = new PythonEngine();
engine.Execute("myString = 'hello'");
Assert.AreEqual("hello reader", engine.Evaluate("myString + ' reader'"));

That was pretty easy; we executed some python code to assign the
value hello to myString, and then evaluated the expression - sweet
you might say - no effort required.

Now, you could write your scripting engine so that it passed the
strings to the engine for evaluation every time you wanted to
evaluate them - but this strings malarkey isn't very pleasant...
what we really want is a decent god fearing .Net delegate, so we
can call this without having to think about the python engine....
Lets check out our first destination, method delegates.

Method Delegates

Given a converter delegate like this:


(Which by the way, if you haven't stumbled across the generic
ConverterTInput,TOutput> delegate yet,
effectively you end up with a delegate method of the
definition"TOutput Converter(TInput)" - pretty
handy actually)


We could do this:

public void StatementsToStronglyTypedDelegate()
PythonEngine engine = new PythonEngine();
List parameters = new List(new string[] {"age"});
Converter converter =
engine.CreateMethod<>>("return str(age+1)", parameters);
Assert.AreEqual("11", converter(10));

Using a strongly typed overload for the engine's
CreateMethod method, we're able to evaluate statements using
our new delegate, which in turn uses our IronPython method we
created earlier... looks promising!


Now delegates are cool,  but it's only half the story for
scripting in an application - depending on your model, you may be
aiming to produce results similar to a microsoft's VBA in
applications like Excel or Word - and for this we need to be able
to assign python code to events on our own classes... we can do
this using delegates of course, or we could let the python (user
code) do this itself, and save some time.... So lets have a look at
the latter:

public void HookingToEvents()
PythonEngine engine = new PythonEngine();

ManualResetEvent waitHandle = new ManualResetEvent(false);
WebClient client = new WebClient();

List results = new List();

engine.Globals["client"] = client;
engine.Globals["results"] = results;

@"def storeResult(sender, e):

# assign out storeResult function as an event handler for the client class
client.DownloadStringCompleted += storeResult

new Uri(

Assert.IsTrue(waitHandle.WaitOne(10000, false), "timeout occured after 10 seconds");

Assert.AreEqual(1, results.Count);



This test is a bit clunky, but you get the idea... we are:
  • Creating a web client, for downloading some xml from a web
  • Set the client as a global variable for the default module in
    the python engine.
  • Execute some python, which creates a function, and assigns
    that function as a handle for the web client's
    DownloadStringCompleted event (take note at how concise the code
    is, this would be a lot uglier in C#)

  • start the async download
  • Make sure we got a response, and that the python code did
    what it should.

All in all, with a little finesse you can recreate a model
similar to VBA, driving your extension points from events - and
this certainly has some merit - obviously you want to create the
code in their own modules, as opposed to using the default module
for the python engine as we are.

We haven't quite finished with delegates yet though, I'll leave
that for part 2 - which I'll post shortly.

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Batching everywhere....

It seems like batching is a data access "theme" at the moment (much like Castle, IOC & IronPython are all themes in the NZ Blogspace at the moment... even though none of them could be considered new, I've been using Castle IoC container for 1 & 1/2 years now!) - no sooner do I discover the batching support in the Rhino.Commons library, it appears NHibernate now supports it in the latest beta drop and it's a planned feature for the upcoming version 3 of the enterprise library ... It's interesting that this support never made it's way into the framework itself for version 2.0, it's all but there.

On the flip side, for NHibernate at least, the performance boons of batching are impressive (see below for an image from Ayende's blog where he's done some profiling), I haven't checked out in a while, but I wonder if Alex James has had a chance to implement batching support yet? - maybe I should make that my task for the weekend (checking out again that is heh... not implementing support ;o)

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Splicer version Alpha Released

Over the past couple of days I've been working on using DirectShow
and DES (DirectShow Editing Services) for re-encoding mobile video
content suitable for posting on the web... With the goal of
including video editing into our unified "media engine" which the
Syzmk line of products makes use of... as an off-shoot of that work
I decided to refactor the rather ugly code we had for working with
DES over the weekend into something a little less ugly, that hid
most of the details away, say hello to:

(sorry, couldn't resist the lame web 2.0 logo ;o)

A simple little library for doing most of the useful things in DES,
the project is hosted here
up on Codeplex.  It's currently in an
alpha state, at version - and should get feature drops
every week or so until I think it can go into beta.

To give an idea of what I'm up to, it's basically just wrapping up
the various DES components and removing alot of the unpleasantness
(ie. you get to deal with human-friendly units of time like
seconds) .. and seperating the concerns of the timeline, and
rendering that timeline into something useful like audio or video
container (currently that's just WAV, AVI & Windows Media
formats).  It's fully functional, but the interfaces at this
point it isn't very stable as I'm likely to refactor the various
interfaces mercilessly till I get it working how I want, so if you
build something with the library now, it's likely to break in the
future (but probably not in major way, it is after all mirroring
the functionality available in DES).   The added bonus of
developing a set of rich wrappers for a lot of this stuff is that I
can mock away the requirement on DES altogether, which is always a
bonus considering how long the units tests currently take to run
for the Syzmk RMP product.

When I get a chance, I'll put up some code examples to demonstrate
how you might use it... At any rate it'll be going through some dog
fooding in the next month or so while I integrate it with the Syzmk
product, so you'll probably here a little more about in the

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I'm back...

After a long hiatus from Blogging, I've returned... hopefully with a vengence, but more likely with a small "vurrrrp" sound... like hot air bubbling up through porridge.

Lets start off with a recap... Spectacles, testacles, wallet and all that jazz.

My name is Alex Henderson, 26 years young, living in Auckland, New Zealand.  I've been working on code since I was knee high, cut my teeth in GW Basic while in primary school, and C++ a few years after that... Now days I tend to spend my hours working in C# code, and my spare time in either .Net and ruby or python when I feel like a change.

For the last year and a half I've been working for a start up company called Seismic Technologies which works in a rather ill-defined space, which I'll probably talk about in posts to come.

The main product I've been working on for Syzmk is the "Rich Media Processor" - it's a message clearing house, geared
towards taking messages with rich content, transforming them, and then distributing them... The messages might be files on a network share, emails, SMS or MMS messages from a phone etc.  It's all about rich content, so a large part of the product deals with transforming the content before furnishing it to line of business
systems - we have been working with companies like XSOL who use our product to use messages from mobile devices to extend their business processes outside of the host organisation.

Before I was working for the Seismic, I was travelling around Asia for 4 months... which was a lot of fun, I hope to visit europe next... Then maybe Japan, Egypt and South America.

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Wiki this wiki that

With the first release of our COM interop SDK for the Syzmk Rich Media Processor (yes, we have clients who want to integrate with the Rich Media Processor from legacy apps) suite coming out last week, I felt it necessary to put some documentation together... internally we've been using FlexWiki sporadically to document what's happening development-wise, iteration feature sets etc. So It made sense to release our documentation on the platform, and offer our clients that ability to augment the documentation where appropriate.

Mixed Reactions

Wiki's get mixed reactions from a lot of developers - some love them, others loathe them. I think it's generally related to two problems:

  • Lack of refactoring
  • Ignoring beautification

A wiki is a living document, its structure should develop in-line with your understanding on the topics - this includes revisiting old topics, pulling content and moving it into new topics etc. If it attempts to document a product then it must be aligned with releases, otherwise you will forever be chasing your tale... If you can't get commitment to this time allocation from management, just don't even bother.

Stale documentation is often worse then no documentation.

Second to that, if the wiki is clunky, poorly formatted, disorganised and generally lacking in beauty... Then it's not a compelling resource for consumers - getting a wiki clean, well organised and aligned with the rest of your web branding seems to go a long way towards encouraging use.

Goodbye FlexWiki

We've been using FlexWiki partly through a loyalty to the .Net platform ( and because internally it's
what we feel most comfortable with when it comes to have to modify or extend products but the project has stalled for now and just doesn't reach our needs for a commercially capable collaboration tool... (for instance it doesn't support attachments) ... so I decided to go find a new wiki... of which there are many... to many you might say!

WikiMatrix to the rescue

At which point I discovered wikimatrix: - What a great little site! Especially there new Wiki Choice Wizard.. In about 5 minutes I managed to narrow down what I was looking for, and eventually selected TWiki ( as our prime candidate (Confluence also looked very good, but the entry cost didn't seem justifiable at this point).

Hello TWiki

TWiki does have some pitfalls for a Microsoft-focused house, mainly that hosting it on windows is possible but going to cause
tears before bed time... luckily they have a debian vmware installation... so we have avoided all the grief involved with
windows, and gained a tasty performance bonus over running it on windows (Because the project would have required the cygwin tools & apache for windows... not necessarily a high-performance combination)

The second best thing since sliced bread

VMWare server being free has to be probably the best thing since sliced bread (Though I guess unbundling supersedes that for most IT people in NZ of late) - as we're seeing a host of Linux based products being released as pre-configured VM's - suitable as drop in "software appliances" - with a lot less support problems then the normal process of installing Linux onto a virtual machine and setting up the software itself... and Often the memory foot print of the Linux distro + product is half that of an empty windows 2003 standard install, before you've deployed any applications onto it.

So within 15 minutes I had downloaded the 220mb virtual image, booted it up and started editing wiki documents... It's not all quite that easy though, you still need to get your hands dirty doing a little shell based configuration if you want to securely host it on the web - but it's all pretty painless especially if youve dabbled with Linux in the past.

As for TWiki itself - so far it seems very very good, my only dislike is some of the wiki-text conventions it uses, such as the elaborate header mark-up... though FlexWiki was no better - why they couldn't use the Confluence style mark-up of "h1. " through "h6." I'll never know still the wysiwyg editor takes away most of the mark-up pain for new users.

I've managed to avoid doing any Kriss Kross "wickety whack" references for the whole post too - be grateful ;o)

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