Monday, December 21, 2009

Why IronPython?

This is a short article I wrote for the UK MSDN Flash newsletter (a Microsoft newsletter for developers). Unfortunately the online versions of these newsletters aren't being updated at the moment; so instead of linking to it I'm reproducing it here.

Why IronPython?

One of the new features in .NET 4.0 is the dynamic keyword, building on the Dynamic Language Runtime. A major reason for dynamic is to enable easier interaction with dynamic languages like IronPython. But if you're a dyed in the wool C# or VB.NET programmer why should you be interested in IronPython?

Much of the discussion here applies to other dynamic languages, including IronRuby, but Python is my particular area of expertise.

IronPython is a .NET implementation of the popular open source programming language Python. Python is an expressive language that is easy to learn and supports several different programming styles; interactive, scripting, procedural, functional, object oriented and metaprogramming. But what can you do with IronPython that isn't already easy with your existing tools?

The first entry in the list of programming styles is 'interactive'. The IronPython distribution includes ipy.exe, the executable for running scripts or programs that also doubles as an interactive interpreter. When you run ipy.exe you can enter Python code that is evaluated immediately and the result returned. It is a powerful tool for exploring assemblies and learning how to use new frameworks and classes by working with live objects.

The second reason to use IronPython is also the second programming style in the list; scripting. Python makes an excellent tool for generating XML from templates, automating build tasks and a host of other everyday operations. Because scripts can be executed without compilation experimentation is simple and fast. Python often creeps into businesses as a scripting language, but beware it spreads!

One of the big use cases for IronPython is for embedding in applications. Potential uses include user scripting, adding a live console for debugging, creating domain specific languages where rules can be added or modified at runtime or even building hybrid applications using several languages. Python has several features, like the ability to customise attribute access, that make it particularly suited to the creation of lightweight DSLs. IronPython has been designed with these uses in mind and has a straightforward hosting API.

There are many areas where dynamic languages are fundamentally different from statically typed languages, a topic that rouses strong opinions. Here are a few features of IronPython that make it easy to develop with:
  • No type declarations
  • First class and higher order functions
  • No need for generics, flexible container types instead
  • Protocols and duck-typing instead of compiler enforced interfaces
  • First class types and namespaces that can be modified at runtime
  • Easier to test than statically typed languages
  • Easy introspection (reflection without the pain)
  • Problems like covariance, contravariance and casting just disappear
The best way to learn how to get the best from IronPython is my book IronPython in Action. I've also written a series of articles aimed at .NET developers to help get you started including Introduction to IronPython, Python for .NET Programmers and Tools and IDEs for IronPython.

Happy experimenting!

Michael Foord

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