[Python.NET] Embedded Python .Net example - running scripts

[Ron Harding]

Did you try background or threadpool threads? Redirected process calls and looking for stdin stdout stderr streams allows more control.

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  On Wed, Oct 3, 2018 at 15:47, Luke, Steve<Steve.Luke at moldev.com> wrote:    <!--#yiv5337413704 P {margin-top:0;margin-bottom:0;}-->


I am getting a crash trying to embed Python into my VB program using Python for .NET. The goal of my application is to allow users to run their own python scripts inside a larger application. The crash I am getting happens the second time I run a script that imports certain large libraries (like numpy or scikit-image) but does not affect all libraries (for example PIL).
 
  
 
My environment:
 
Windows 10 Pro x64, Python 3.6.5 (in Anaconda), Python for .Net 2.4.0 (installed from git’s master branch).
 
  
 
Here is the VB code:
 
   PublicFunction Startup(ByRef param AsString)AsInteger
 
       PythonEngine.Initialize()
 
       'mm.PrintMsg(PythonEngine.BuildInfo)
 
       'mm.PrintMsg(PythonEngine.Compiler)
 
       'mm.PrintMsg(PythonEngine.Platform)
 
       'mm.PrintMsg(PythonEngine.ProgramName)
 
       'mm.PrintMsg(PythonEngine.PythonHome)
 
       'mm.PrintMsg(PythonEngine.PythonPath)
 
       Using (Py.GIL())
 
  
 
           Dim scriptPath AsString = param
 
  
 
           Dim scriptDir AsString = Path.GetDirectoryName(scriptPath)
 
           Dim scriptName AsString = GetPythonModuleName(scriptPath)
 
           Dim scriptParam AsString = ""
 
  
 
           Dim scriptScope As PyScope = Py.CreateScope()
 
  
 
           Dim scriptText AsString = My.Computer.FileSystem.ReadAllText(scriptPath)
 
           scriptScope.Exec(scriptText)
 
  
 
           If scriptScope.Contains(STARTUP_METHOD_NAME) Then
 
               scriptScope.Exec(String.Format("{0}(r'{1}')", STARTUP_METHOD_NAME, scriptParam))
 
           EndIf
 
  
 
           scriptScope.Dispose()
 
       EndUsing
 
       PythonEngine.Shutdown()
 
  
 
       Return 0
 
   EndFunction
 
  
 
And this is the Python script I am running:
 
import skimage.io
 
  
 
defStartup(param):
 
   pass
 
  
 
defDocommand(param):
 
   pass
 
   
 
defShutdown():
 
   pass
 
  
 
When I run it the VB code the first time, things work great. When I run the VB code a second time (without first restarting the entire application) I get an access violation exception on the scriptScope.Exec() call:
 
Exception: System.AccessViolationException :
 
Message: Attempted to read or write protected memory. This is often an indication that other memory is corrupt.
 
Source: Python.Runtime
 
StackTrace:
 
  at Python.Runtime.Runtime.PyObject_Call(IntPtr pointer, IntPtr args, IntPtr kw)
 
  at Python.Runtime.ImportHook.__import__(IntPtr self, IntPtr args, IntPtr kw)
 
  at Python.Runtime.Runtime.PyObject_Call(IntPtr pointer, IntPtr args, IntPtr kw)
 
  at Python.Runtime.ImportHook.__import__(IntPtr self, IntPtr args, IntPtr kw)
 
  at Python.Runtime.Runtime.PyObject_Call(IntPtr pointer, IntPtr args, IntPtr kw)
 
  at Python.Runtime.ImportHook.__import__(IntPtr self, IntPtr args, IntPtr kw)
 
  at Python.Runtime.Runtime.PyObject_Call(IntPtr pointer, IntPtr args, IntPtr kw)
 
  at Python.Runtime.ImportHook.__import__(IntPtr self, IntPtr args, IntPtr kw)
 
  at Python.Runtime.Runtime.PyObject_Call(IntPtr pointer, IntPtr args, IntPtr kw)
 
  at Python.Runtime.ImportHook.__import__(IntPtr self, IntPtr args, IntPtr kw)
 
  at Python.Runtime.Runtime.PyObject_Call(IntPtr pointer, IntPtr args, IntPtr kw)
 
  at Python.Runtime.ImportHook.__import__(IntPtr self, IntPtr args, IntPtr kw)
 
  at Python.Runtime.Runtime.PyObject_Call(IntPtr pointer, IntPtr args, IntPtr kw)
 
  at Python.Runtime.ImportHook.__import__(IntPtr self, IntPtr args, IntPtr kw)
 
  at Python.Runtime.Runtime.PyObject_Call(IntPtr pointer, IntPtr args, IntPtr kw)
 
  at Python.Runtime.ImportHook.__import__(IntPtr self, IntPtr args, IntPtr kw)
 
  at Python.Runtime.Runtime.PyObject_Call(IntPtr pointer, IntPtr args, IntPtr kw)
 
  at Python.Runtime.ImportHook.__import__(IntPtr self, IntPtr args, IntPtr kw)
 
  at Python.Runtime.Runtime.PyRun_String(String code, IntPtr st, IntPtr globals, IntPtr locals)
 
  at Python.Runtime.PyScope.Exec(String code, IntPtr _globals, IntPtr _locals)
 
  at MyApp.MyClass.Startup(String& param) in C:\Git\MyPath\MyApp.vb:line 132
 
  Unfortunately the stack trace doesn't show line numbers for anything in the Python.Runtime.
 
  
 
Interestingly, if you look at the VB code, I have some lines of commented out code:
 
       'mm.PrintMsg(PythonEngine.BuildInfo)
 
       'mm.PrintMsg(PythonEngine.Compiler)
 
       'mm.PrintMsg(PythonEngine.Platform)
 
       'mm.PrintMsg(PythonEngine.ProgramName)
 
       'mm.PrintMsg(PythonEngine.PythonHome)
 
       'mm.PrintMsg(PythonEngine.PythonPath)
 



Since the app doesn’t have a console, this sends the text to the enclosing app for display. If I uncommon that code, then the first time I run it I get:
 
default, Mar 29 2018, 13:32:41
 
[MSC v.1900 64 bit (AMD64)]
 
win32
 
python
 
  
 
F:\Anaconda3\python36.zip;F:\Anaconda3\Lib;F:\Anaconda3\DLLs;C:\MX6
 
  
 
And the second time I run it I get:
 
default, Mar 29 2018, 13:32:41
 
[MSC v.1900 64 bit (AMD64)]
 
win32
 
pyth???
 
???
 
F:\Anaconda3\python36.zip;F:\Anaconda3\Lib;F:\Anaconda3\DLLs;C:\MX6
 
  
 
And the application doesn’t crash! Instead it just says the skimage module can’t be found. Notice the bolded lines (bold added after the fact). The program name and python home values are being corrupted.
 
Is there something I am doing wrong as far as taking down the PythonEngine such that it could be put back up in an as-new state later on?
 








Steve





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