Pass variable from C# - IronPython to a Python script

Question

I have a WPF application. For the purpose of this question, let's say it's a simple Window with a button. When I click on that button, I would like a Python script to be executed. Therefore, I went looking around and found out that I can run Python scripts using IronPython. Part1 works well, it runs the python scripts. From what I've gathered from looking around the web, Part2 is what I should do if I want to call a specific method.

private void btnWhatever_Click(object sender, RoutedEventArgs e)
{ 
    //Basic engine to run python script. - Part1
    ScriptEngine engine = Python.CreateEngine();
    string pythonScriptPath = System.IO.Path.GetDirectoryName(System.IO.Path.GetDirectoryName(System.IO.Directory.GetCurrentDirectory()));        
    ScriptSource source = engine.CreateScriptSourceFromFile(pythonScriptPath + "/python.py");
    ScriptScope scope = engine.CreateScope();
    source.Execute(scope); 

    //Part2
    Object myclass = engine.Operations.Invoke(scope.GetVariable("pythonScriptClass"));
    object[] parameters = new object[] { "Hi",3 };
    engine.Operations.InvokeMember(myclass, "theMethod", parameters);
}

The problem is, I kept getting 'Microsoft.Scripting.ArgumentTypeException' happened in Microsoft.Dynamic.dll : theMethod() takes exactly 2 arguments (3 given).

I understand from that error that I'm giving 3 arguments instead of 2 but I can't call a specific method another way from what I found out. I'm pretty new to IronPython and Python in general but here is a script example :

class pythonScriptClass:

def swapText(text, number):
    return text[number:] + text[:number]

def getLetterIndex(letter, text):
    for k in range(len(text)):
        if (letter== text[k]):
            return k
    return -1

def theMethod(text , number):
    result= swapText("textToBeSwaped", number)
    toBeReturned  = ""
    for letter in text:
        if letter in "abcdefghijklmnopqrstuvwxyz":
            toBeReturned  = toBeReturned  + result[getLetterIndex(letter, result)]           
    return toBeReturned

My ultimate goal for the moment is to get this to work and therefore be able to call theMethod() from the Python script and get the returned value using C# - IronPython.

I have tried other methods such as : scope.SetVariable("key","value"); but I got the same error.

Know little about IronPython, but how is object[] parameters with new object[] { "Hi",3 } is interpreted in Python? It looks 2-length but treated as 3-length, possibly "H", "i" and "3"? What happens with {"foo", 3}? — dytori
– dytori, Commented Mar 15, 2016 at 7:34
Sorry for the delay @dytori . To answer your question, it does the same thing with "foo". — Marks
– Marks, Commented Mar 15, 2016 at 21:28
Sorry, I overlooked you were using a class signature. See my answer. — dytori
– dytori, Commented Mar 16, 2016 at 6:55

dytori · Accepted Answer · 2016-03-16 06:54:48Z

1

As for python member method, the first argument is self.

class pythonScriptClass:
  def theMethod(self, text, number):
    # and call self.swapText(...)

This is why the number of arguments went wrong.

answered Mar 16, 2016 at 6:54

dytori

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2 Comments

Marks Over a year ago

It worked like a charm. Thank you ! I'll have to go check more about those member / non-member methods...

dytori Over a year ago

Member method may not be a proper term... Please check instance / class / static method in Python.

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