C++ with Python embedding: crash if Python not installed

In addition to pythonxy.dll, you also need the entire Python library, i.e. the contents of the lib folder, plus the extension modules, i.e. the contents of the DLLs folder. Without the standard library, Python won't even start, since it tries to find os.py (in 3.x; string.py in 2.x). On startup, it imports a number of modules, in particular site.py.

There are various locations where it searches for the standard library; in your cases, it eventually finds it in the registry. Before, uses the executable name (as set through Py_SetProgramName) trying to find the landmark; it also checks for a file python31.zip which should be a zipped copy of the standard library. It also checks for a environment variable PYTHONHOME.

You are free to strip the library from stuff that you don't need; there are various tools that compute dependencies statically (modulefinder in particular).

If you want to minimize the number of files, you can

1. link all extension modules statically into your pythonxy.dll, or even link pythonxy.dll statically into your application
2. use the freeze tool; this will allow linking the byte code of the standard library into your pythonxy.dll.
3. (alternatively to 2.) use pythonxy.zip for the standard library.

Nice. And if you do not want to zip, copy Python26\DLLs & Python26\lib to your exe directory as:

.\myexe.exe       
.\python26.dll
.\Python26\DLLs
.\Python26\lib

And then set PYTHONHOME with Py_SetPythonHome() API. Apparently, this API is not in the list of "allowed" calls before Py_Initialize();

Below worked for me on Windows (Python not installed):

#include "stdafx.h"
#include <iostream>
#include "Python.h"

using namespace std;

int _tmain(int argc, _TCHAR* argv[])
{
   char pySearchPath[] = "Python26";
   Py_SetPythonHome(pySearchPath);
   Py_Initialize();
   PyRun_SimpleString("from time import time,ctime\n"
                     "print 'Today is',ctime(time())\n");
   //cerr << Py_GetPath() << endl;
   Py_Finalize();

    return 0;
}

Good that the search path is relative w.r.t the exe. Py_GetPath can show you where all it is looking for the modules.