Add function to __builtin__ module through C API
Sometimes it need to embedding a Python script to a C code, and it references to a function, which also provided by the same C code. Then you have to import the module, as you defined in your C code.
But this import would be skipped, if you add your function to your __builtin__ module. In Python3 (3.5), there is the PyModule_AddFunctions() function, but in the previous versions, you can make it like this snippet.
See these recipes:
Makefile: https://code.activestate.com/recipes/579111-add-function-to-__builtin__-module-through-c-api-c/
Python script: https://code.activestate.com/recipes/579112-add-function-to-__builtin__-module-through-c-api-c/
C, 141 lines
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Copy to clipboard1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 | #include <stdio.h>
#include <Python.h>
PyObject *pName, *pModule, *pFunc;
PyObject *builtin, *builtinname, *builtin_dict, *myfunc;
/* python mymodule */
static PyObject*
mymodule_usleep(PyObject *self, PyObject *args)
{
unsigned long i;
if (!PyArg_ParseTuple(args, "k:usleep", &i)) {
return NULL;
}
usleep(i);
return Py_None;
}
static char mymodule_usleep_doc[] =
"usleep(unsigned long) - Sleep for the specified number of microseconds.";
static PyMethodDef mymodule_methods[] = {
{"usleep", mymodule_usleep, METH_VARARGS, mymodule_usleep_doc},
{NULL, NULL}
};
/* python mymodule */
int
pyinit(char * pfile)
{
char syspath[255], pwd[255];
char fname[] = "bar";
Py_Initialize();
/* need for add pwd directory */
PyRun_SimpleString("import sys");
strcpy(syspath, "sys.path.append('");
if (getcwd(pwd, sizeof(pwd)) != NULL) {
strcat(syspath, pwd);
}
strcat(syspath, "')");
PyRun_SimpleString(syspath);
/* add new function to __builtin__ module */
// http://stackoverflow.com/questions/6565175/adding-new-command-to-module-through-c-api
// Python3: https://mail.python.org/pipermail/python-list/2015-October/697917.html
pName = PyString_FromString("__builtin__");
builtin = PyImport_Import(pName);
builtinname = PyString_FromString("__builtin__");
builtin_dict = PyModule_GetDict(builtin);
myfunc = PyCFunction_NewEx(&mymodule_methods[0], (PyObject*)NULL, builtinname);
PyDict_SetItemString(builtin_dict, "usleep", myfunc);
Py_DECREF(pName);
/* end of new function adding */
/* load Own python script */
pName = PyString_FromString(pfile);
PyErr_Print();
pModule = PyImport_Import(pName);
Py_DECREF(pName);
if (pModule != NULL) {
pFunc = PyObject_GetAttrString(pModule, fname);
if (pFunc && PyCallable_Check(pFunc)) {
return 0;
}
else {
if (PyErr_Occurred()) {
PyErr_Print();
}
fprintf(stderr, "Cannot find function \"%s\"\n", fname);
Py_XDECREF(pFunc);
Py_XDECREF(pModule);
Py_XDECREF(builtin);
Py_XDECREF(builtinname);
Py_XDECREF(builtin_dict);
Py_XDECREF(myfunc);
return 1;
}
}
else {
PyErr_Print();
fprintf(stderr, "Failed to load \"%s\"\n", pfile);
return 1;
}
return 0;
}
void myloop() {
int rc, var1, var2;
PyObject *mydict, *pArgs, *pValue;
printf("Enter numbers:");
rc = scanf("%d %d", &var1, &var2);
while (rc == 2) {
mydict = Py_BuildValue("{sisi}","a", var1, "b", var2);
pArgs = PyTuple_New(1);
PyTuple_SetItem(pArgs, 0, mydict);
pValue = PyObject_CallObject(pFunc, pArgs);
Py_DECREF(pArgs);
if (pValue != NULL) {
printf("Result of call: %ld\n", PyInt_AsLong(pValue));
Py_DECREF(pValue);
}
else {
PyErr_Print();
fprintf(stderr,"Call failed\n");
}
Py_DECREF(mydict);
printf("Enter numbers: ");
rc = scanf("%d %d", &var1, &var2);
}
}
int main(int argc, char **argv) {
if (argc < 2) {
fprintf(stderr, "Usage: call pythonfile\n");
return 1;
}
if (pyinit(argv[1]) == 0) {
myloop();
Py_DECREF(pFunc);
Py_DECREF(pModule);
Py_DECREF(builtin);
Py_DECREF(builtinname);
Py_DECREF(builtin_dict);
Py_DECREF(myfunc);
}
Py_Finalize();
return 0;
}
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