Modules/operator module

Source:

cpython 3.14 @ ab2d84fe1023/Modules/_operator.c ↗

The operator module exposes Python's built-in operators as first-class functions. It is heavily used by functools, itertools, and sorting code.

Map

Category	Functions
Arithmetic	add, sub, mul, truediv, floordiv, mod, pow, neg, pos, abs
Bitwise	and_, or_, xor, invert, lshift, rshift
Comparison	lt, le, eq, ne, ge, gt
In-place	iadd, isub, imul, ... (all correspond to +=, -=, etc.)
Sequence	getitem, setitem, delitem, concat, contains, indexOf, countOf
Object	attrgetter, itemgetter, methodcaller
Type checks	is_, is_not, truth, not_
Misc	index, length_hint

Reading

Simple operators

// CPython: Modules/_operator.c:62 op_add
static PyObject *
op_add(PyObject *s, PyObject *a)
{
    PyObject *a1, *a2;
    if (!PyArg_UnpackTuple(a, "add", 2, 2, &a1, &a2))
        return NULL;
    return PyNumber_Add(a1, a2);
}

Each arithmetic function is a thin wrapper around the abstract object API (PyNumber_*, PyObject_*).

attrgetter

// CPython: Modules/_operator.c:440 attrgetter_call
static PyObject *
attrgetter_call(attrgetterobject *ag, PyObject *args, PyObject *kw)
{
    PyObject *obj;
    if (!PyArg_UnpackTuple(args, "attrgetter", 1, 1, &obj))
        return NULL;
    if (ag->nattrs == 1)
        return PyObject_GetAttr(obj, ag->attr);
    /* multiple attrs: return a tuple */
    PyObject *result = PyTuple_New(ag->nattrs);
    for (Py_ssize_t i = 0; i < ag->nattrs; i++)
        PyTuple_SET_ITEM(result, i, PyObject_GetAttr(obj, ag->attrs[i]));
    return result;
}

Dotted access (operator.attrgetter('a.b.c')) is split on . and applied iteratively.

itemgetter

// CPython: Modules/_operator.c:550 itemgetter_call
static PyObject *
itemgetter_call(itemgetterobject *ig, PyObject *args, PyObject *kw)
{
    PyObject *obj;
    if (!PyArg_UnpackTuple(args, "itemgetter", 1, 1, &obj))
        return NULL;
    if (ig->nitems == 1)
        return PyObject_GetItem(obj, ig->item);
    /* multiple items: return a tuple */
    ...
}

itemgetter is the workhorse for sorted(data, key=itemgetter('name')) patterns.

length_hint

// CPython: Modules/_operator.c:745 op_length_hint
static PyObject *
op_length_hint(PyObject *module, PyObject *args)
{
    PyObject *obj;
    Py_ssize_t default_value = 0;
    if (!PyArg_ParseTuple(args, "O|n:length_hint", &obj, &default_value))
        return NULL;
    Py_ssize_t hint = PyObject_LengthHint(obj, default_value);
    ...
    return PyLong_FromSsize_t(hint);
}

PyObject_LengthHint tries __len__ first, then __length_hint__. This is used by list() to pre-allocate storage.

gopy notes

operator functions are in module/operator/. The attrgetter, itemgetter, and methodcaller types need to be proper callable objects with __reduce__ support for pickle compatibility (used by multiprocessing and concurrent.futures).