Mailman 3 November 2003 - Python.NET

Using an existing Python installation
by Mike Casaday 25 Feb '04

25 Feb '04

Python for .NET is really cool! Here's something I found out while trying to get it to work with my existing Python 2.3 installation. The README says: > **Can I use it with my existing Python installation?** > > Yes, at least on win32 systems. Just copy the files > Python.Runtime.dll and CLR.dll from the PythonNet directory to the > root directory of your python installation. > This answer comes with one caveat in my experience. For some reason you have to 'import CLR' before trying to import anything else from the .NET runtime. This isn't the case if I use the Python executable included in PythonNet-1.0-beta1.tgz, only if I use my existing Python installation. So this fails: from CLR.System.Reflection import Assembly Assembly.LoadWithPartialName('SomeNamespace') import CLR.SomeNamespace as SomeNamespace But this works: import CLR from CLR.System.Reflection import Assembly Assembly.LoadWithPartialName('SomeNamespace') import CLR.SomeNamespace as SomeNamespace Is it possible I'm doing something wrong (more than likely)? Is this a bug? Is this expected behavior? ZODB requires you to 'import ZODB' before you do certain things, so I wouldn't be surprised... ______________ mike P.S. I'm now playing around with the TrueVision3D game engine using Python, something that I couldn't really do until now. I'm happy I saw a link to this project from Daily Python-URL.

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a demo program using ASP .Net and Python for .Net
by Yan Weng 25 Nov '03

25 Nov '03

Hi all, I wrote a small program to illustrate how to embed Python engine in Asp .Net using Python for .Net. If you are interested in that, take a look of this site http://s89292973.onlinehome.us/research.htm . If you find the demo is useful or have some questions about that, please contact with me at wengyan(a)hotmail.com or yweng(a)cs.uoregon.edu . :-) Best regards, Yan 412-421-6958 wengyan(a)hotmail.com http://www.cs.uoregon.edu/~yweng

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hosted interpreter
by Keith J. Farmer 20 Nov '03

20 Nov '03

Is there a simple example of hosting the Python interpreter in a .NET form? I'm thinking something similar to PyShell/PyCrust in wxPython.

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RE: example of calling Python from C# with simple object marshalling
by MBarclay＠cri-inc.com 20 Nov '03

20 Nov '03

Yes, overloading Invoke() for PyObjects sounds like a better solution than adding a Portal class. That is so much simpler. It's complete signature should probably be: public object[] Invoke(params object[] objects) This way, with a single method, you can pass down to Python nothing, a single primitive value, or a bunch of them (0, 1, *). Regarding your first overload (object Invoke(...) as opposed to object[] Invoke(...)), I don't believe you can overload by return type alone (maybe I'm thinking in C++), but that would be fine because the overload you indicated that returns an object is less important than the one that returns an object list (with the latter you can achieve what the former does, with the additional utility of being able to return an empty object list to mean "null" where a primitive type would otherwise be expected). The other method... object ToObject(); would be worth having as publics also, in fact I suppose it would nicely encapsulate what the new Invoke() method(s) need to do their internal stuff. Just a nitpick: I don't think you can compile: int i = thing.ToObject() as Int32 ...since "i" is a value type, and the 'as' operator can only be used on reference types (value types cannot hold null). But I get your point... int i = (Int32)thing.ToObject(); // this will throw an exception if the conversion is not valid Mark Barclay Sr. Software Engineer CRi Inc. "Brian Lloyd" <brian(a)zope.co To: <MBarclay(a)cri-inc.com> m> cc: <pythondotnet(a)python.org> Subject: RE: example of calling Python from C# with simple object 11/19/2003 marshalling 02:50 PM I think this points out an area still wanting in the embedding interface (calling into Python and getting back managed objects rather than PyObject wrappers). I'm thinking that a good start would be a variation on what your example does as an overload for the Invoke method of PyObjects: object Invoke(...) object[] Invoke(...) I think it would also be a good idea to have a 'ToObject' method on PyObjects: object ToObject(); which would: - if the Python object represents a managed object, return that object - if the Python object is a primitive type that is convertible to a managed primitive type, return the converted value - otherwise throw an exception Another option could be to have PyObject implement IConvertible, though that would be more work, and might not buy you anything over using: int i = thing.ToObject() as Int32 thoughts? Brian Lloyd brian(a)zope.com V.P. Engineering 540.361.1716 Zope Corporation http://www.zope.com

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Python for .NET 1.0 beta 3 released
by Brian Lloyd 20 Nov '03

20 Nov '03

Python for .NET 1.0 beta 3 has been released - you can download it from: http://www.zope.org/Members/Brian/PythonNet/ Python for .NET is a near-seamless integration of Python with the .NET common language runtime. For more details, see the README: http://www.zope.org/Members/Brian/PythonNet/README.html The beta 3 release fixes a startup issue that has been affecting people on some platforms. There is also now a mailing list for discussion, questions and issues related to Python for .NET at: pythondotnet(a)python.org. To subscribe to the mailing list or read the online archives, see: http://mail.python.org/mailman/listinfo/pythondotnet Brian Lloyd brian(a)zope.com V.P. Engineering 540.361.1716 Zope Corporation http://www.zope.com

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very newbie installation question
by Hawkeye Parker 20 Nov '03

20 Nov '03

apologies in advance for this one, but i'm very new to .net: do you need .net (1.1) installed to run python for .net? or is the entire clr "built" into python for .net? to put it another way, do you need anything aside from the python for .net tarball to run python for .net? thanks hawkeye

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trouble with windows servers
by Hawkeye Parker 19 Nov '03

19 Nov '03

i've managed to get python.net up and running on win2k, but when i try to run it in my server environment (Windows 2003 server), python.exe crashes: Application has generated an exception that could not be handled. Process id=0xd38 (3384), Thread id=0xd40 (3392). cmd traceback: Unhandled Exception: System.Runtime.InteropServices.COMException (0x80070006): T he handle is invalid. at System.Runtime.InteropServices.Marshal.ThrowExceptionForHR(Int32 errorCode , IntPtr errorInfo) at System.Runtime.InteropServices.Marshal.FreeHGlobal(IntPtr hglobal) at Python.Runtime.StaticMethodWrapper..ctor(Type obType, String name) at Python.Runtime.ImportHook.Initialize() at Python.Runtime.Runtime.Initialize() at Python.Runtime.PythonEngine.Initialize() at PythonConsole.Main(String[] args) any ideas why or how to fix? thanks, hawkeye parker QA Software Engineer Autodesk, Inc

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example of calling Python from C# with simple object marshalling
by MBarclay＠cri-inc.com 19 Nov '03

19 Nov '03

In case anyone is trying to use the embedding aspect of this fine package (well-done, Brian!), here is a quick-and-dirty starting point that shows how one might call a Python function with a variable argument list of .NET simple value types (e.g. int, double, string) returning an object list, from a .NET application. The in and out lists are ordinary simple type objects in the NET wold, and ordinary Python objects in the Python world. Note that this is not meant to replace anything Brian has in the Runtime DLL. It is simply a proof of concept test I did to begin discovering what I can do in the C# -> Python direction. The following trivial python file has an invoke() method which can be called from C# in a very uncluttered way... """ PyPortal.py demonstration of passing simple type arguments and returning a tuple of simple types """ def invoke(a1, a2): print 'invoke() called with %s and %s.' % (a1, a2) # show that we can return a list of simple types... return ("[wrap(%s)]" % s, f*2) The C# code that calls this looks like this, including a traversal of the returned objects.... PythonEngine.Initialize(); PyObject pyportal = PythonEngine.ImportModule("PyPortal"); PyObject callable = pyportal.GetAttr("invoke"); Portal portal = new Portal(); object[] objects = portal.Invoke(callable, "Mark Barclay", 123.456); if (objects != null) { foreach (object o in objects) { if (o != null) Console.WriteLine(o.ToString()); else Console.WriteLine("o is null."); } } Note the object instantiation "Portal portal = new Portal()". For this to work, the following in-lined file, Portal.cs, needs to be added to the runtime (I created a project PyWrapper in VS2003 that includes all the sources from src\runtime), because it needs internal visibility into some of the classes there (e.g. Converter). There is almost certainly a better, simpler way, but for now this showed me that calling Pythoin with arbitrary value type args and retuning a list of Python objects onverted to .NET objects was feasible using Python for .NET. A class such as this (Portal) might be a handy addition to the runtime, or maybe Brian has something like that there already, or on the drawing board. If not, I'd be happy to take on the task of creating a more complete and robust implementation of this, if anyone thinks it would be useful. (Please forgive the lack of comments, error detection and general completeness in the following demonstration code) using System; namespace Python.Runtime { public class Portal { public Portal() { } public object[] Invoke(PyObject callable, params object[] objects) { if (!callable.IsCallable()) { throw new Exception("Invoke called with an un-callable"); } int size = objects.Length; IntPtr items = Runtime.PyTuple_New(size); for (int i=0; i<size; i++) { IntPtr po = Converter.ToPythonImplicit(objects[i]); Runtime.PyTuple_SetItem(items, i, po); } PyTuple tuple = new PyTuple(items); PyObject pyresult = callable.Invoke(tuple); if (pyresult.Handle == Runtime.PyNone) { return new object[] { "__none__" }; } if (PyTuple.IsTupleType(pyresult)) { int size_out = pyresult.Length(); object [] objects_out = new object[size_out]; for (int i=0; i<size_out; i++) { try { PyObject po = pyresult[i]; IntPtr obj = po.Handle; Type type = typeof(Object); if (Runtime.PyFloat_Check(obj)) { type = typeof(double); } else if (Runtime.PyInt_Check(obj)) { type = typeof(int); } else if (Runtime.PyString_Check(obj)) { type = typeof(string); } else { objects_out[i] = "[unknown type]"; break; } object mo = null; bool setError = true; bool ok = Converter.ToManaged(po.Handle, type, out mo, setError); if (ok) { objects_out[i] = mo; //Console.WriteLine(mo.ToString()); } } catch (Exception ex) { Console.WriteLine(ex.Message + "\r\n" + ex.StackTrace); objects_out[i] = "?"; } } return objects_out; } // just testing return new object[] { 123, "abc" }; } } } Please let me know if this is of any help, or if it is entirely redundant (perhaps I missed something in the API that does just this). Mark Barclay Sr. Software Engineer CRi Inc.

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Form design
by david Powell 19 Nov '03

19 Nov '03

I have been exploring the use of the free C# IDE from www.icsharpcode.net. As well as designing a form for C#, you can design a form and save it as xml. A new XmlForm can be created by the menu sequence File,New,File,Misc,XmlForm. I have written a module to convert the xml file to a python class that references PythondotNet. This class will draw the component controls on the form but does not have any event handlers. The name of the class is taken from the name element of the xmlForm. It seemed to me desirable to leave this generated class untouched. Another class can inherit the generated class and add the event procedures. I attach 1. the xmlForm, Form1.xfrm 2. the python equivalent, Form1.py 3. the derived class and main function, App1.py 4. the module PythondotNetForms.py that contains the conversion function XMLToPythondotNet(filenameXML,filenamePythondotNet) this module uses Frederik Lundh's ElementTree to process the xml. The function XMLToPythondotNet contains a dictionary of properties mapped to property type. This could be expanded. Alternatively properties not set in the conversion could be set programmatically afterwards. Pythonistas may find my code ugly. I have a VB.net mindset. David Powell

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pythondotnet beta 2 initialization error.
by J Stauft 18 Nov '03

18 Nov '03

Hello: I am not sure if this is a bug, or just me attempting to run code on a platform it was not designed for but ... Here is the traceback I get when I attempt to display the 'helloform.py' using the python version shipped with the .tar.gz __________________________________________________________ C:\Desktop\PythonNet-1.0-beta2>python.exe .\demo\helloform.py Unhandled Exception: System.ArgumentException: The parameter is incorrect. at System.Runtime.InteropServices.Marshal.ThrowExceptionForHR(Int32 errorCode , IntPtr errorInfo) at System.Runtime.InteropServices.Marshal.FreeHGlobal(IntPtr hglobal) at Python.Runtime.StaticMethodWrapper..ctor(Type obType, String name) at Python.Runtime.ImportHook.Initialize() at Python.Runtime.Runtime.Initialize() at Python.Runtime.PythonEngine.Initialize() at PythonConsole.Main(String[] args) C:\Desktop\PythonNet-1.0-beta2> ___________________________________________________________ I get the same traceback with PythonNet-1.0-beta1 , however, both PythonNet-preview1 and PythonNet-preview2 continue to work fine ( at least for the limited testing performed). I am running Windows 98 (fully updated from Microsoft) using Win4Lin on top of i386 linux , kernel 2.2.18. I have only one version of python on the 'virtual' machine (2.3.2) -- installed using the standard python.org. installer. The .NET Framework version is 1.1.4322 Any thoughts or suggestions? Sincerely, J

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