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

[Denis Akhiyarov]

Please search the issue tracker on github for shutdown related issues. This
was discussed extensively.

There is WIP pull request worked on by 3 people to support this reloading
scenario in Unity.


On Wed, Oct 3, 2018, 9:50 PM Ron Harding via PythonDotNet <
pythondotnet at python.org> wrote:

> Did you try background or threadpool threads? Redirected process calls and
> looking for stdin stdout stderr streams allows more control.
>
> Sent from Yahoo Mail on Android
> <https://go.onelink.me/107872968?pid=InProduct&c=Global_Internal_YGrowth_AndroidEmailSig__AndroidUsers&af_wl=ym&af_sub1=Internal&af_sub2=Global_YGrowth&af_sub3=EmailSignature>
>
> On Wed, Oct 3, 2018 at 15:47, Luke, Steve
> <Steve.Luke at moldev.com> wrote:
>
> 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:
>
>     Public Function Startup(ByRef param As String) As Integer
>
>         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 As String = param
>
>
>
>             Dim scriptDir As String = Path.GetDirectoryName(scriptPath)
>
>             Dim scriptName As String = GetPythonModuleName(scriptPath)
>
>             Dim scriptParam As String = ""
>
>
>
>             Dim scriptScope As PyScope = Py.CreateScope()
>
>
>
>             Dim scriptText As String =
> 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))
>
>             End If
>
>
>
>             scriptScope.Dispose()
>
>         End Using
>
>         PythonEngine.Shutdown()
>
>
>
>         Return 0
>
>     End Function
>
>
>
> And this is the Python script I am running:
>
> import skimage.io
>
>
>
> def Startup(param):
>
>     pass
>
>
>
> def Docommand(param):
>
>     pass
>
>
>
> def Shutdown():
>
>     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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