I embedded python in my C++ program.
I use PyImport_ImportModule to load my module written in a .py file. But how can I load it from memory? Let's say my .py file is encrypted, so I need to first decrypt it and feed the code to python to execute.
Moreover, it'd be nice if I could bypass/intercept or modify the import mechanism, so that doesn't load modules from the filesystem but my own memory blocks, how/can I do that?
The following example shows how to define a module from a C string:
#include <stdio.h>
#include <Python.h>
int main(int argc, char *argv[])
{
Py_Initialize();
PyRun_SimpleString("print('hello from python')");
// fake module
char *source = "__version__ = '2.0'";
char *filename = "test_module.py";
// perform module load
PyObject *builtins = PyEval_GetBuiltins();
PyObject *compile = PyDict_GetItemString(builtins, "compile");
PyObject *code = PyObject_CallFunction(compile, "sss", source, filename, "exec");
PyObject *module = PyImport_ExecCodeModule("test_module", code);
PyRun_SimpleString("import test_module; print(test_module.__version__)");
Py_Finalize();
return 0;
}
output:
hello from python
version: 2.0
You can read about import hooks in the docs. You will need to define a class with find_module and load_module methods. Something like the following should work:
PyObject* find_module(PyObject* self, PyObject* args) {
// ... lookup args in available special modules ...
return Py_BuildValue("B", found);
}
PyObject* load_module(PyObject* self, PyObject* args) {
// ... convert args into filname, source ...
PyObject *builtins = PyEval_GetBuiltins();
PyObject *compile = PyDict_GetItemString(builtins, "compile");
PyObject *code = PyObject_CallFunction(compile, "sss", source, filename, "exec");
PyObject *module = PyImport_ExecCodeModule("test_module", code);
return Py_BuildValue("O", module);
}
static struct PyMethodDef methods[] = {
{ "find_module", find_module, METH_VARARGS, "Returns module_loader if this is an encrypted module"},
{ "load_module", load_module, METH_VARARGS, "Load an encrypted module" },
{ NULL, NULL, 0, NULL }
};
static struct PyModuleDef modDef = {
PyModuleDef_HEAD_INIT, "embedded", NULL, -1, methods,
NULL, NULL, NULL, NULL
};
static PyObject* PyInit_embedded(void)
{
return PyModule_Create(&modDef);
}
int main() {
...
PyImport_AppendInittab("embedded", &PyInit_embedded);
PyRun_SimpleString("\
import embedded, sys\n\
class Importer:\n\
def find_module(self, fullpath):\n\
return self if embedded.find_module(fullpath) else None\n\
def load_module(self, fullpath):\n\
return embedded.load_module(fullpath)\n\
sys.path_hooks.insert(0, Importer())\n\
");
...
}
