使用C语言扩展Python程序的简单入门指引

class refcount:
  # etc.
r1 = refcount() # 引用计数为1
r2 = r1     # 引用计数为2
del(r1)     # 引用计数为1
del(r2)     # 引用计数为0，删除对象

// build an integer
PyObject* pInt = Py_BuildValue("i", 2003);
assert(PyInt_Check(pInt));
int i = PyInt_AsLong(pInt);
Py_DECREF(pInt);
// build a float
PyObject* pFloat = Py_BuildValue("f", 3.14f);
assert(PyFloat_Check(pFloat));
float f = PyFloat_AsDouble(pFloat);
Py_DECREF(pFloat);
// build a string
PyObject* pString = Py_BuildValue("s", "Python");
assert(PyString_Check(pString);
int nLen = PyString_Size(pString);
char* s = PyString_AsString(pString);
Py_DECREF(pString);

// create the tuple
PyObject* pTuple = PyTuple_New(3);
assert(PyTuple_Check(pTuple));
assert(PyTuple_Size(pTuple) == 3);
// set the item
PyTuple_SetItem(pTuple, 0, Py_BuildValue("i", 2003));
PyTuple_SetItem(pTuple, 1, Py_BuildValue("f", 3.14f));
PyTuple_SetItem(pTuple, 2, Py_BuildValue("s", "Python"));
// parse tuple items
int i;
float f;
char *s;
if (!PyArg_ParseTuple(pTuple, "ifs", &i, &f, &s))
  PyErr_SetString(PyExc_TypeError, "invalid parameter");
// cleanup
Py_DECREF(pTuple);

// create the list
PyObject* pList = PyList_New(3); // new reference
assert(PyList_Check(pList));
// set some initial values
for(int i = 0; i < 3; ++i)
  PyList_SetItem(pList, i, Py_BuildValue("i", i));
// insert an item
PyList_Insert(pList, 2, Py_BuildValue("s", "inserted"));
// append an item
PyList_Append(pList, Py_BuildValue("s", "appended"));
// sort the list
PyList_Sort(pList);
// reverse the list
PyList_Reverse(pList);
// fetch and manipulate a list slice
PyObject* pSlice = PyList_GetSlice(pList, 2, 4); // new reference
for(int j = 0; j < PyList_Size(pSlice); ++j) {
 PyObject *pValue = PyList_GetItem(pList, j);
 assert(pValue);
}
Py_DECREF(pSlice);
// cleanup
Py_DECREF(pList);

// create the dictionary
PyObject* pDict = PyDict_New(); // new reference
assert(PyDict_Check(pDict));
// add a few named values
PyDict_SetItemString(pDict, "first", 
           Py_BuildValue("i", 2003));
PyDict_SetItemString(pDict, "second", 
           Py_BuildValue("f", 3.14f));
// enumerate all named values
PyObject* pKeys = PyDict_Keys(); // new reference
for(int i = 0; i < PyList_Size(pKeys); ++i) {
 PyObject *pKey = PyList_GetItem(pKeys, i);
 PyObject *pValue = PyDict_GetItem(pDict, pKey);
 assert(pValue);
}
Py_DECREF(pKeys);
// remove a named value
PyDict_DelItemString(pDict, "second");
// cleanup
Py_DECREF(pDict);

int fact(int n)
{
 if (n <= 1) 
  return 1;
 else 
  return n * fact(n - 1);
}

#include <Python.h>
PyObject* wrap_fact(PyObject* self, PyObject* args) 
{
 int n, result;
 
 if (! PyArg_ParseTuple(args, "i:fact", &n))
  return NULL;
 result = fact(n);
 return Py_BuildValue("i", result);
}
static PyMethodDef exampleMethods[] = 
{
 {"fact", wrap_fact, METH_VARARGS, "Caculate N!"},
 {NULL, NULL}
};
void initexample() 
{
 PyObject* m;
 m = Py_InitModule("example", exampleMethods);
}

PyObject* method(PyObject* self, PyObject* args);

PyObject* method(PyObject *self, PyObject *args) 
{
 Py_INCREF(Py_None);
 return Py_None;
}

[xiaowp@gary code]$ gcc -fpic -c -I/usr/include/python2.2 \
          -I /usr/lib/python2.2/config \
          example.c wrapper.c
[xiaowp@gary code]$ gcc -shared -o example.so example.o wrapper.o

[xiaowp@gary code]$ python
Python 2.2.1 (#1, Aug 30 2002, 12:15:30)
[GCC 3.2 20020822 (Red Hat Linux Rawhide 3.2-4)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import example
>>> example.fact(4)
24
>>>