[IronPython] Building via AST

Justin Chase justin.m.chase at gmail.com
Wed Apr 14 20:23:38 CEST 2010

I feel like I'm sooooo close but something isn't quite working. Here is my
current code:

var runtime = Python.CreateRuntime();

var engine = runtime.GetEngineByFileExtension(".py");
var context = (PythonContext)HostingHelpers.GetLanguageContext(engine);

var globals = new PythonDictionary();
globals.Add("__name__", "<test>"); // I get an exception without this.

var options = new PythonCompilerOptions(ModuleOptions.ExecOrEvalCode |
var unit = new SourceUnit(context, NullTextContentProvider.Null, "",

var moduleContext = new ModuleContext(globals, context);
var codeContext = new CodeContext(
new PythonDictionary(),

var classDefinition = new IronPython.Compiler.Ast.ClassDefinition(
new Expression[] { },
new FunctionDefinition(
new[] { new Parameter("self") },
new ReturnStatement(new ConstantExpression("hello python!"))));

var pythonAst = new PythonAst(
new IronPython.Compiler.Ast.SuiteStatement(new Statement[] { /* import, */
classDefinition }),
new CompilerContext(
new ThrowsErrorSink()));

var lambda = (System.Linq.Expressions.LambdaExpression)pythonAst.Reduce();
var func = (Func<CodeContext, FunctionCode, object>)lambda.Compile();
var result = func(codeContext, null); // result is null

dynamic python = HostingHelpers.CreateScriptScope(engine,
*dynamic example = python.Example(); // fails! Example is not in scope.*

Can anyone tell me what I'm missing? This has got to be pretty close.

On Mon, Apr 12, 2010 at 7:51 PM, Justin Chase <justin.m.chase at gmail.com>wrote:

> Awesome.  I will thanks.
> On Apr 12, 2010 7:49 PM, "Dino Viehland" <dinov at microsoft.com> wrote:
>  This might be possible.  If you wrap this all up in a PythonAst object
> (calling the constructor which takes a CompilerContext), call Bind on it
> then you should get a LambdaExpression back out.  You can Compile() on
> that.
> But it’s not like this is well traveled territory and this only applies to
> 2.6.1 (before that the trees weren’t DLR ASTs so they weren’t reducable).
> When we do this ourselves we also call the produced delegate and flow in
> some data.  The delegate is going to want at least a FunctionCode object as
> an argument but I think you could get away with passing null (at least as
> long as no exceptions are thrown).  The delegate might also want a
> CodeContext object as well depending on the compilation mode we end up using
> (which is based on the CompilerContext you give us).  This you wouldn’t be
> able to get away w/ passing null.  But you can get one by doing new
> ModuleContext(new PythonDictionary(), pythonContext).GlobalContext.  The
> HostingHelpers class can give you a LanguageContext from the ScriptEngine
> for Python which you can cast to a PythonContext.
> Let me know if it works! J
> *From:* users-bounces at lists.ironpython.com [mailto:
> users-bounces at lists.ironpython.com] *On Behalf Of *Justin Chase
> *Sent:* Monday, April 12, 2010 4:09 PM
> To: Discussion of IronPython Subject: Re: [IronPython] Building via AST
>    Ok, so at risk of being a nuissance I have one last question because I
> feel like I'm half way t...
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Justin Chase
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