_operator.c: itemgetter, attrgetter, methodcaller, and operator wrappers

_operator is the C accelerator imported by Lib/operator.py via from _operator import *. The pure-Python fallbacks defined earlier in that file are overwritten by these faster C implementations.

Map

Lines	Symbol	Role
68–400	_operator_*_impl functions	Binary and unary arithmetic (add, sub, mul, floordiv, …)
400–600	In-place variants _operator_i*_impl	iadd, isub, imul, … routed through PyNumber_InPlace*
600–700	Comparison and logical wrappers	eq, ne, lt, le, gt, ge, truth, not_, is_, is_not
700–800	length_hint, _compare_digest, call	Misc helpers
1016–1234	itemgetterobject, itemgetter_new, itemgetter_call_impl	Single and multi-key subscript callable
1234–1601	attrgetterobject, attrgetter_new, dotted_getattr, attrgetter_call_impl	Dotted-attribute chain callable
1601–1942	methodcallerobject, methodcaller_new, methodcaller_call	Named-method-plus-frozen-args callable
1951–2000	operator_exec	Module init: register all entries in module dict

Reading

truth, not_, is_, is_not: logical wrappers

These four are 1- or 2-argument wrappers around PyObject_IsTrue and identity comparison. truth(a) calls PyObject_IsTrue(a) and returns True or False. not_(a) negates it. is_(a, b) and is_not(a, b) compare raw pointer identity rather than value equality.

The gopy port wraps each as a unaryFunc or binaryFunc closure that delegates to objects.IsTruthy or pointer equality. 3.14 added is_none and is_not_none as optimized variants; both are present in module/_operator/module.go at the {"is_none", ...} and {"is_not_none", ...} entries.

dotted_getattr and attrgetter_call_impl

attrgetter_new (line 1262) splits each argument string on "." and stores the segments. At call time, dotted_getattr walks the chain with repeated PyObject_GetAttr calls:

for (i = 0 ; i < nattrs; ++i) {
    tmp = PyObject_GetAttr(obj, PyTuple_GET_ITEM(dotted, i));
    Py_DECREF(obj);
    if (tmp == NULL) return NULL;
    obj = tmp;
}

A single-attribute attrgetter returns the value directly; a multi-attribute one returns a tuple, one entry per chain. The gopy dottedGetattr helper (line 856) is a direct port: iterate chain []string, call objects.GetAttr at each step, propagate errors immediately.

itemgetter_call_impl: single vs. multi key

When constructed with a single key, itemgetter stores just that key and itemgetter_call_impl calls PyObject_GetItem(obj, key) directly. With multiple keys it stores a tuple and returns a new tuple of PyObject_GetItem(obj, keys[i]) results. The gopy port (itemgetterCall, line 742) uses the same branch: len(ig.items) == 1 returns a scalar, otherwise a *objects.Tuple.

gopy notes

• All arithmetic operators are fully ported. Each delegates to the corresponding objects.Number* function rather than using a custom implementation, keeping the single source of truth in the objects layer.
• _compare_digest performs a constant-time byte comparison to resist timing attacks; the gopy port uses Go's subtle.ConstantTimeCompare.
• 3.14 introduced is_none and is_not_none as first-class entries; both are registered in buildModule.
• Pickling support (__reduce__) is implemented for all three callable types, matching the CPython itemgetter_reduce, attrgetter_reduce, and methodcaller_reduce functions.