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Objects/boolobject.c

cpython 3.14 @ ab2d84fe1023/Objects/boolobject.c

Objects/boolobject.c defines PyBool_Type and the True/False singletons. bool is a subclass of int: True has ob_ival = 1 and False has ob_ival = 0. This means all integer operations work on booleans automatically.

Map​

LinesSymbolRole
1-40_Py_FalseStruct, _Py_TrueStructStatic singleton objects
41-80bool_newReturns True or False; never allocates
81-130bool_repr, bool_and, bool_or, bool_xorOverride &/`
131-160PyBool_Type definitionType slots

Reading​

Singleton enforcement​

bool_new converts any value to a bool by calling PyObject_IsTrue and returning the pre-existing singleton. Subclassing bool is allowed but calling the subclass constructor still returns a bool instance (not the subclass), which is the documented behaviour.

// CPython: Objects/boolobject.c:55 bool_new
static PyObject *
bool_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
    ...
    ok = PyObject_IsTrue(x);
    if (ok < 0) return NULL;
    return PyBool_FromLong(ok);
}

bool_and / bool_or / bool_xor​

These override int's bitwise operators to return a bool when both operands are bool. If either operand is a plain int, the int operation is used and returns an int.

// CPython: Objects/boolobject.c:88 bool_and
static PyObject *
bool_and(PyObject *a, PyObject *b)
{
    if (!PyBool_Check(a) || !PyBool_Check(b))
        return PyLong_Type.tp_as_number->nb_and(a, b);
    return PyBool_FromLong(
        (a == Py_True) & (b == Py_True));
}

bool as int​

True + True == 2, True * 3 == 3. The arithmetic is inherited from PyLong_Type with no overrides. Only __repr__ and the three bitwise operators are overridden.

gopy notes​

True and False are singletons in objects/. bool inherits from int, so arithmetic on booleans returns int. The PyBool_Check predicate maps to py.IsBool(obj) in gopy.