I use D7 with Python4Delphi. After users have imported much of py-files, Python have all these modules cached. I need a way to reset Py engine. So that Py "forgets" all user-imported modules, and I have "clean" Python, w/out restarting the app. How to do it?
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Hmm, good luck with that. I believe you have zero chance of success. Once Python is in your process, in my experience, it's there for good.David Heffernan– David Heffernan2014-01-30 18:02:51 +00:00Commented Jan 30, 2014 at 18:02
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2 Answers
There is a demo showing you how to unload/reload python using P4D at https://github.com/pyscripter/python4delphi/tree/master/PythonForDelphi/Demos/Demo34. The key method that (re)creates the python components and (re)loads different versions of python is shown below:
procedure TForm1.CreatePythonComponents;
begin
if cbPyVersions.ItemIndex <0 then begin
ShowMessage('No Python version is selected');
Exit;
end;
// Destroy P4D components
FreeAndNil(PythonEngine1);
FreeAndNil(PythonType1);
FreeAndNil(PythonModule1);
{ TPythonEngine }
PythonEngine1 := TPythonEngine.Create(Self);
PyVersions[cbPyVersions.ItemIndex].AssignTo(PythonEngine1);
PythonEngine1.IO := PythonGUIInputOutput1;
{ TPythonModule }
PythonModule1 := TPythonModule.Create(Self);
PythonModule1.Name := 'PythonModule1';
PythonModule1.Engine := PythonEngine1;
PythonModule1.ModuleName := 'spam';
with PythonModule1.Errors.Add do begin
Name := 'PointError';
ErrorType := etClass;
end;
with PythonModule1.Errors.Add do begin
Name := 'EBadPoint';
ErrorType := etClass;
ParentClass.Name := 'PointError';
end;
{ TPythonType }
PythonType1 := TPythonType.Create(Self);
PythonType1.Name := 'PythonType1';
PythonType1.Engine := PythonEngine1;
PythonType1.OnInitialization := PythonType1Initialization;
PythonType1.TypeName := 'Point';
PythonType1.Prefix := 'Create';
PythonType1.Services.Basic := [bsRepr,bsStr,bsGetAttrO,bsSetAttrO];
PythonType1.TypeFlags :=
[tpfHaveGetCharBuffer,tpfHaveSequenceIn,tpfHaveInplaceOps,
tpfHaveRichCompare,tpfHaveWeakRefs,tpfHaveIter,tpfHaveClass,tpfBaseType];
PythonType1.Module := PythonModule1;
PythonEngine1.LoadDll;
end;
The demo uses the unit PythonVersions to discover installed python versions.
Comments
It should be sufficient to destroy and re-create the TPythonEngine object:
OriginalOwner := GetPythonEngine.Owner;
GetPythonEngine.Free;
TPythonEngine.Create(OriginalOwner);
Destroying it calls Py_Finalize, which frees all memory allocated by the Python DLL.
Or, if you're just using the Python API without the VCL wrappers, you can probably just call Py_NewInterpreter on your TPythonInterface object to get a fresh execution environment without necessarily discarding everything done before.
8 Comments
David Heffernan
In my experience this will not yield good results. Have you experienced success in booting Python out like that?
David Heffernan
@david inability to load new python instances
Prog1020
@Rob Did you test it with TPythonModule, TPythonGuiInputOutput, are they reinited ok? I test myself later.
Rob Kennedy
Haven't tested anything, @Alextp. I don't have Delphi. I only read the documentation and looked at the source code.
David Heffernan
@alextp My Python embedding experience is with the raw C API and not this Delphi wrapper. I have tried very hard to remove the Python engine from the process, and then bring it back. I failed. This is not to say that I am sure it cannot be done, just that I think you should be prepared for failure. The docs suggest that this should be possible, with some caveats: docs.python.org/2/c-api/init.html
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