Hello,

I am trying to write a program that is embedding the python interpreter in order to execute python code. I don't need to transfer values between pascal and python.

More specifically, I'm trying to convert to pascal the following:

#include <Python.h>
int main(int argc, char *argv[])
{
  Py_Initialize();
  PyRun_SimpleString("from time import time,ctime\n"
                     "print 'Today is',ctime(time())\n");
  Py_Finalize();
  return 0;
}

I have a minimal unit which includes the needed functions (h2pas wasn't able to convert the Python.h , and i only need those 3 functions anyway ) :

unit Python;
interface
  uses Strings;
  {$LinkLib python2.4}
{$IFDEF FPC}
{$PACKRECORDS C}
{$ENDIF}
  procedure Py_Initialize;external name 'Py_Initialize';
  procedure Py_Finalize;external name 'Py_Finalize';
  function PyRun_SimpleString(_para1:Pchar):longint; external name
'PyRun_SimpleString';
implementation
end.

The pascal program is :

var cmd: PChar;
begin
   cmd:=StrAlloc(256);
   Py_Initialize();
   StrPCopy(cmd, 'print "Hello"');
   PyRun_SimpleString(cmd);   { <--- the program crashes here :
runtime error 216 }
   Py_Finalize();
end.

The problem is that the program crashes at execution with "Runtime error 216 at <a_memory_address> ". The backtrace is :

(gdb) backtrace
#0 0xb7e6c3fa in PyOS_Readline () from /usr/lib/libpython2.4.so.1.0 #1 0xb7e6ca7b in PyTokenizer_FromFile () from /usr/lib/libpython2.4.so.1.0 #2 0xb7e6cf5d in PyTokenizer_FromString () from /usr/lib/libpython2.4.so.1.0 #3 0xb7e69fb3 in PyParser_ParseStringFlagsFilename () from /usr/lib/libpython2.4.so.1.0
#4 0xb7e6a091 in PyParser_ParseStringFlags ()
from /usr/lib/libpython2.4.so.1.0
#5 0xb7eeb408 in PyParser_SimpleParseStringFlags () from /usr/lib/libpython2.4.so.1.0
#6 0xb7eeb8a1 in PyRun_StringFlags () from /usr/lib/libpython2.4.so.1.0 #7 0xb7eecba3 in PyRun_SimpleStringFlags () from /usr/lib/libpython2.4.so.1.0 #8 0xb7eecc21 in PyRun_SimpleString () from /usr/lib/libpython2.4.so.1.0 #9 0x08048324 in main () at runpy.pas:16

What am i doing wrong ? Any idea ?

Thank you,
Adrian Maier

Try addign cdecl or stdcall at the end

procedure Py_Initialize;external name 'Py_Initialize'; cdecl; // or stdcall;
procedure Py_Finalize;external name 'Py_Finalize'; cdecl; // or stdcall;

Leonardo M. Ramé
http://leonardorame.blogspot.com

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I created a Python.pas unit this way using Delphi and it works correctly (note the cdecl directive before external):

unit python;
interface
  procedure Py_Initialize; cdecl; external 'python24.dll';
  procedure Py_Finalize; cdecl; external 'python24.dll';
  function PyRun_SimpleString(_para1:Pchar):longint; cdecl; external 'python24.dll';
implementation
end.

Leonardo M. Ramé
http://leonardorame.blogspot.com

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Thanks Leonardo !

The trick was to add cdecl _before_ external :

function PyRun_SimpleString(_para1:Pchar):longint; cdecl; external
name 'PyRun_SimpleString';

I had initially added cdecl _after_ the 'external' clause , but this generated an
error ( directive CDECL has conflicts with other directives ) which confused me into thinking that cdecl was not needed.

Thanks,
Adrian Maier

Adrian Maier ha scritto:

you welcome!

If you are using Lazarus on Windows, I can send you the core units of Python for Delphi adapted in order to be compiled with Lazarus (not yet usable under Free Pascal only).

references: http://membres.lycos.fr/marat/delphi/python.htm

If you need using pure Free Pascal (RTL+FCL), or are on Linux or MacOS, this has to be done in other ways, but the P4D library is the model to follow.

There is another idea to explore:
With Python 2.5 there is a module named "ctypes" that allows calling DLL functions from Python. And we know how to build a DLL with FPC, true?.

I (on windows) and my friend (on Linux) are actually working in order to make some experiment and documentation about this matter. If you could partecipate and help...

bye
tiziano

I'm on Linux . Thanks anyway !

It's good to know about this. But this is a solution for the opposite problem: calling pascal code from python.

Cheers,
Adrian Maier

Adrian Maier ha scritto:

yes, it's another problem (just to puntualize).

Anyway, mainly, we also are trying to call Python from pascal on Linux.

bye
tiziano