كتابة وحدة امتداد C لـ Python

بنية امتداد C

// myext.c skeleton
#include <Python.h>

static PyObject* say_hello(PyObject* self, PyObject* args) {
    Py_RETURN_NONE;
}

static PyMethodDef methods[] = {
    {"say_hello", say_hello, METH_NOARGS, "Print hello"},
    {NULL, NULL, 0, NULL}
};

static struct PyModuleDef module = {
    PyModuleDef_HEAD_INIT, "myext", NULL, -1, methods
};

PyMODINIT_FUNC PyInit_myext(void) {
    return PyModule_Create(&module);
}

تحليل المعاملات

static PyObject* add(PyObject* self, PyObject* args) {
    int a, b;
    if (!PyArg_ParseTuple(args, "ii", &a, &b))
        return NULL;
    return PyLong_FromLong(a + b);
}

إعادة القيم

// Return a Python tuple (int, float)
static PyObject* stats(PyObject* self, PyObject* args) {
    int n = 10;
    double avg = 5.0;
    return Py_BuildValue("(id)", n, avg);
    // Py_BuildValue format: i=int d=double s=str
}

عدّ المراجع

static PyObject* make_list(PyObject* self, PyObject* args) {
    PyObject* lst = PyList_New(3);
    for (int i = 0; i < 3; i++) {
        // PyList_SET_ITEM steals the reference:
        PyList_SET_ITEM(lst, i, PyLong_FromLong(i));
    }
    return lst;   // caller owns the list
}

إطلاق الاستثناءات

static PyObject* safe_div(PyObject* self, PyObject* args) {
    int a, b;
    if (!PyArg_ParseTuple(args, "ii", &a, &b)) return NULL;
    if (b == 0) {
        PyErr_SetString(PyExc_ZeroDivisionError, "division by zero");
        return NULL;
    }
    return PyLong_FromLong(a / b);
}

setup.py لامتدادات C

# setup.py
from setuptools import setup, Extension

setup(
    name="myext",
    ext_modules=[
        Extension(
            "myext",
            sources=["myext.c"],
            extra_compile_args=["-O2"],
        )
    ]
)
# python setup.py build_ext --inplace
# import myext; myext.add(3, 4)

استخدام الامتداد المُنشأ

# After: python setup.py build_ext --inplace
import myext
print(myext.add(3, 4))        # 7
print(myext.safe_div(10, 2))  # 5
# myext.safe_div(1, 0)         # ZeroDivisionError

المعاملات المسماة

static char* kwargs[] = {"x", "y", NULL};

static PyObject* hypot_c(PyObject* self,
                          PyObject* args,
                          PyObject* kw) {
    double x, y;
    if (!PyArg_ParseTupleAndKeywords(args, kw, "dd",
                                     kwargs, &x, &y))
        return NULL;
    return PyFloat_FromDouble(sqrt(x*x + y*y));
}

الثوابت على مستوى الوحدة

PyMODINIT_FUNC PyInit_myext(void) {
    PyObject* m = PyModule_Create(&module);
    if (!m) return NULL;
    PyModule_AddIntConstant(m, "VERSION", 1);
    PyModule_AddStringConstant(m, "AUTHOR", "Alice");
    return m;
}

تحرير GIL

static PyObject* heavy(PyObject* self, PyObject* args) {
    long n;
    if (!PyArg_ParseTuple(args, "l", &n)) return NULL;
    long result;
    Py_BEGIN_ALLOW_THREADS
        result = slow_c_computation(n);  // GIL released
    Py_END_ALLOW_THREADS
    return PyLong_FromLong(result);
}

اختبار الامتداد

# test_myext.py
import pytest
import myext

def test_add(): assert myext.add(3, 4) == 7
def test_zero_div():
    with pytest.raises(ZeroDivisionError):
        myext.safe_div(1, 0)

تحقق سريع

مراجعة