# Embedding Python APT

This is a very basic tutorial for working with the C++ bindings.

## Basics

To use the python-apt C++ bindings, first include the `python-apt/python-apt.h` header:

    #include <python-apt/python-apt.h>

Now, the module needs to be initialized. This is done by calling the function `import_apt_pkg()`. This function returns 0 on success and a negative value in case of failure:

    if (import_apt_pkg() < 0)
        return;

## Longer example

The following code will create a standalone application which provides a module `client` with the attribute `hash` which stores an object of the type `apt_pkg.HashString`:

    /*
     * client-example.cc - A simple example for using the python-apt C++ API.
     *
     * Copyright 2009 Julian Andres Klode <jak@debian.org>
     *
     * This program is free software; you can redistribute it and/or modify
     * it under the terms of the GNU General Public License as published by
     * the Free Software Foundation; either version 2 of the License, or
     * (at your option) any later version.
     *
     * This program is distributed in the hope that it will be useful,
     * but WITHOUT ANY WARRANTY; without even the implied warranty of
     * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     * GNU General Public License for more details.
     *
     * You should have received a copy of the GNU General Public License
     * along with this program; if not, write to the Free Software
     * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
     * MA 02110-1301, USA.
     */

    #include <python-apt/python-apt.h>
    #include <apt-pkg/hashes.h>

    // The module initialization.
    extern "C" void initclient() {
        if (import_apt_pkg() < 0)
            return;
        // Initialize a module.
        PyObject *Module = Py_InitModule("client", NULL);

        // Create a HashString, which will be added to the module.
        HashString *hash = new HashString("0966a120bb936bdc6fdeac445707aa6b");
        // Create a Python object for the hashstring and add it to the module
        PyModule_AddObject(Module, "hash", PyHashString_FromCpp(hash, false, NULL));

        // Another example: Add the HashString type to the module.
        Py_INCREF(&PyHashString_Type);
        PyModule_AddObject(Module, "HashString", (PyObject*)(&PyHashString_Type));
    }

    int main(int argc, char *argv[]) {
        // Return value.
        int ret = 0;
        // Initialize python
        Py_Initialize();
        // Make the client module importable
        PyImport_AppendInittab("client", &initclient);
        // Set the commandline arguments.
        PySys_SetArgv(argc, argv);

        // Import the module, so the user does not have to import it.
        if (PyRun_SimpleString("import client\n") < 0) {
            // Failure (should never be reached)
            ret = 1;
            goto end;
        }

        // Run IPython if available, otherwise a normal interpreter.
        if (PyRun_SimpleString("from IPython.Shell import start\n") == 0)
            PyRun_SimpleString("start(user_ns=dict(client=client)).mainloop()\n");
        else
            Py_Main(argc, argv);

    end:
        Py_Finalize();
        return ret;
    }

If this file were called client-example.cc, you could compile it using:

    g++ -lapt-pkg -lpython2.5 -I/usr/include/python2.5 -o client client-example.cc