Embedding IronPython – C# Calling Python Script Part 1

Friday, 8 June 2007

Embedding IronPython is quite trivial and is documented here.

You can call functions in the embedded python module by
(1) retrieving the function using Evaluate()
(2) then apply the function using the Call() method

using (IronPython.Hosting.PythonEngine engine
  = new IronPython.Hosting.PythonEngine())
{
  engine.Execute(@"
  def foo(a, b):
    return a+b*2");

  // (1) Retrieve the function
  IronPython.Runtime.Calls.ICallable foo
   = (IronPython.Runtime.Calls.ICallable) engine.Evaluate("foo");

  // (2) Apply function
  object result = foo.Call(3, 25);
}

The ICallable.Call method can only be called varargs-style, and can’t be called using keyword arguments.
(This is probably a bug.)

Call(params object[] args)

To use keyword arguments, you’ll need to cast the function into PythonFunction.

Note:
Unfortunately, Python classes aren’t CLR classes, and couldn’t be accessed directly or subclassed by C# by referencing a built assembly. You’ll have to go through the hosting interfaces to get an instance of the class.

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The entry 'Embedding IronPython – C# Calling Python Script Part 1' was posted on June 8th, 2007 at 10:21 pm and last modified on June 6th, 2008 at 9:13 pm, and is filed under IronPython, Python. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

3 Responses to “Embedding IronPython – C# Calling Python Script Part 1”

  1. Greg writes:
    No. 1 — June 4th, 2008 at 3:53 am

    Simple and informative, thank you!

  2. Peter Morris writes:
    No. 2 — May 19th, 2010 at 1:31 am

    May I ask for your advice/help?

    I have a C# app which I need to load user defined formula from a database and executed them in order to get results. It would look something like this

    foreach customer (about 100 of them)
    {
    Load about 20 formulas and stick them in a dictionary keyed by a GUID
    foreach employee of the customer (about 10,000 of them)
    {
    employee.X = the result of formula 1
    employee.Y = the result of formula 2
    etc
    }
    }

    Someone has suggested I embed IronPython, but being a complete newbie I have no idea what I am doing. In addition I need to

    1: Ensure the formula returns a decimal value by compiling it (not running it) so I can validate the user’s input.
    2: Access values from the DB via some kind of custom method, such as GetValue(“Order total”)

    Could you help me out please?

    Thanks

  3. Chui writes:
    No. 3 — May 19th, 2010 at 9:57 pm

    Unfortunately, Python is dynamically typed, and you can only check at runtime that each result returned in a decimal value. To achieve step #1, you will have to perform a runtime cast, and trap for errors.

    As for #2, you need to define a C# method called GetValue and follow the steps here http://www.voidspace.org.uk/ironpython/hosting_api.shtml#preloading-assemblies

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