Python C API-功能超载

Question

我有许多C函数接受不同的参数，例如

foo_i(int a)
foo_c(char c)

是否可以在Python C API中超载这些功能？

我尝试使用以下方法表：

static PyMethodDef test_methods[] = {
    {"foo", (PyCFunction)foo_i, METH_VARARGS, "int"},
    {"foo", (PyCFunction)foo_c, METH_VARARGS, "char"},
    {NULL, NULL, 0, NULL}
};

但是，当我调用 foo 从python中，我总是在表底部使用该功能。

关于如何调用 foo_i((和 foo_c((使用 foo((P>

谢谢！

Answer 1

给他们不同的python级别名称，或者编写单个包装器函数，该功能可以检查提供的参数并将其分配到正确的"真实"函数。Python本身没有直接支持基于参数类型的过载功能。

如果您要为您写包装器，则可以看一下pybind11，它确实可以从您尝试的意义上进行重载(它可以通过兜帽下的类型检查包装器，所以它只是句法糖，行为的变化(。

未经测试的示例代码：

static PyObject*
foo_wrapper(PyObject *self, PyObject *arg)
{
    Py_buffer view;
    Py_ssize_t ival;
    // Check for/handle length 1 bytes-like object (bytes, bytearray, small mmap, etc.)
    if (PyObject_GetBuffer(arg, &view, PyBUF_SIMPLE) == 0) {
        if (view.len != 1) {
             PyErr_Format(PyExc_ValueError, "Must receive exactly one byte, got %zd", view.len);
             PyBuffer_Release(&view);
             return NULL;
        }
        foo_c(((char*)view.buf)[0]);
        Py_RETURN_NONE; // Or convert return from foo_c if it exists
    }
    // Check for/handle integer-like object that fits in C int
    PyErr_Clear(); // Ignore error for objects not supporting buffer protocol
    ival = PyNumber_AsSsize_t(arg, PyExc_ValueError);
    if (PyErr_Occurred()) {
        if (PyErr_ExceptionMatches(PyExc_TypeError)) {
            // Replace with general error message about both accepted argument types,
            // since only reporting error from int conversion might confuse folks
            PyErr_Format(PyExc_TypeError, "Argument must be length 1 bytes-like object or integer; received %R", Py_TYPE(arg));
        }
        return NULL;
    }
    // Check valid range (Py_ssize_t often larger than int)
    if (ival < INT_MIN or ival > INT_MAX) {
        return PyErr_Format(PyExc_ValueError, "Integer must be in range [%d-%d]; received %zd", INT_MIN, INT_MAX, ival);
    }
    foo_i((int)ival);
    Py_RETURN_NONE; // Or convert return from foo_i if it exists
}
static PyMethodDef test_methods[] = {
    {"foo", (PyCFunction)foo_wrapper, METH_O, "Wrapper for foo_c and foo_i"},
    {NULL, NULL, 0, NULL}
};