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Delayed startup

rg_becker Posted: Fri Jul 14, 2006 9:34 pm

Joined: 06 Oct 2005

Posts: 7

Delayed startup

For various reasons I`m trying to update some python for delphi code
and am finding it hard to get the output.

The original code started its own python engine after form
initialisation (I think that`s so it can set up dll paths etc etc).

I dropped a memo and a TPythonGUIInputOutput onto my form and
connected output to the memo.

Now in my startup routine I have this code

setEnvironmentVariable(`PYTHONHOME`,pChar(appDir));
pyPath:= self.getPyPathFromDirs(pyDirs);
fEngine:= TMyAtomPythonEngine.Create(nil);

fEngine.io := pyIO; {IO set}

fEngine.dllPath:= appDir; // dir containing python dll
fEngine.pyFlags := [pfNoSite];
fEngine.RedirectIO:= True;
fEngine.loaded;
fEngine.execString(format(`import sys; sys.path[:] =
r"%s".split(";")`, [pyPath]));
// For debugging
fEngine.execString(`print "sys.path =", sys.path`);
fEngine.execString(`print "sys.modules = ", sys.modules`);

but although the app still behaves OK I don`t seem to see prints
coming out in my memo. Debugging reveals that pyIO is the right object
and the engine startup seems to do the right thing.

What am I missing?

Robin Becker

rg_becker Posted: Tue Jul 18, 2006 12:12 am

Joined: 06 Oct 2005

Posts: 7

Delayed startup

--- In pythonfordelphi@yahoogroups.com, "rg_becker" <robin@...> wrote:
.......
> but although the app still behaves OK I don`t seem to see prints
> coming out in my memo. Debugging reveals that pyIO is the right object
> and the engine startup seems to do the right thing.
>
> What am I missing?

... turns out this is a threading issue

Looking in PythonEngine.pas I see that the wrapped stdout/stderr are
not serviced if the current thread is not the main one. A discussion
earlier mentioned this and that a possible solution involved a
separate window to handle a message posting fix. Some of that seems to
be in place now.

It seems that if I use PythonGUIInputOutput with the code in pio_write
modified to avoid the current thread return

ie
if False and (GetCurrentThreadId <> MainThreadId) then

and fix

procedure TPythonInputOutput.AddWrite( const str : String );
begin
FQueue.Add( str );
if FQueue.Count > FMaxLines then
FQueue.Delete(0);
AddPendingWrite;
end;

then I can get the threading test in Demo11 to do lots of output from
Threads 1 2 and 3. Makes the test a bit slower, but I get no problems.
Interestingly if I use delaywrites:=True then I do get a problem in
the message handling.

Robin

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