Modules/arraymodule.c (part 5)

Source:

cpython 3.14 @ ab2d84fe1023/Modules/arraymodule.c ↗

This annotation covers array mutation and conversion. See modules_array4_detail for array.__new__, array.__getitem__, array.__setitem__, and type codes.

Map

Lines	Symbol	Role
1-80	array.append	Add one element to the end
81-160	array.extend	Extend from another array or iterable
161-240	array.frombytes	Append raw bytes
241-320	array.tobytes	Return raw bytes of the array's data
321-600	array.fromlist / tolist	Convert between array and list

Reading

array.append

// CPython: Modules/arraymodule.c:840 array_append_impl
static PyObject *
array_append_impl(arrayobject *self, PyObject *v)
{
    return ins(self, Py_SIZE(self), v);
}

static int
ins(arrayobject *self, Py_ssize_t where, PyObject *v)
{
    if (array_resize(self, Py_SIZE(self) + 1) < 0) return -1;
    memmove(self->ob_item + (where + 1) * self->ob_descr->itemsize,
            self->ob_item + where * self->ob_descr->itemsize,
            (Py_SIZE(self) - where - 1) * self->ob_descr->itemsize);
    return setarrayitem(self, where, v);
}

append is ins at the end, requiring no memmove. ins at other positions shifts elements right. setarrayitem converts the Python object to the array's type code using the type descriptor's setitem function.

array.frombytes

// CPython: Modules/arraymodule.c:1020 array_frombytes_impl
static PyObject *
array_frombytes_impl(arrayobject *self, Py_buffer *buffer)
{
    if (buffer->len % self->ob_descr->itemsize != 0) {
        PyErr_SetString(PyExc_ValueError,
                        "bytes length not a multiple of item size");
        return NULL;
    }
    Py_ssize_t n = Py_SIZE(self);
    Py_ssize_t add = buffer->len / self->ob_descr->itemsize;
    if (array_resize(self, n + add) < 0) return NULL;
    memcpy(self->ob_item + n * self->ob_descr->itemsize,
           buffer->buf, buffer->len);
    Py_RETURN_NONE;
}

frombytes appends raw bytes directly without element-by-element conversion. The byte count must be a multiple of the element size. On big-endian machines, the bytes are interpreted in the machine's native byte order.

array.tobytes

// CPython: Modules/arraymodule.c:1060 array_tobytes_impl
static PyObject *
array_tobytes_impl(arrayobject *self)
{
    return PyBytes_FromStringAndSize(self->ob_item,
                                     Py_SIZE(self) * self->ob_descr->itemsize);
}

tobytes returns the raw binary representation of the array. Combined with frombytes, this is the canonical way to serialize/deserialize arrays to files or sockets without element-by-element conversion.

gopy notes

array.append is module/array.ArrayAppend in module/array/module.go. It appends to a Go typed slice (e.g., []int32 for 'i'). frombytes copies bytes directly via unsafe. tobytes returns []byte as a bytes object.