what singleton means

“one-item tuple”

A flyweight object (... “that is returned by constructor”?)

A singleton object accessed by name

The one unique object that is ever returned

from a class that implements the Gang of Four’s Singleton Pattern.

Lib/pydoc_data/topics.py

technically

you can test for object identity

even where used, discouraged: singleton *object* used instead

we say “None” not “NoneType()” <--- wait, it's not even possible!

ellipsis

None

NotImplemented

(X,) x

UTC

singleton SearchDialog” etc in IDLE, turtle, distutil

string ('') are singletons and cannot be cloned.

Make sure response tuple is a singleton

“CPython's empty tuple is a singleton and cached in” - NO, that’s a flyweight

Python/Python-ast.c:928: Del_singleton = PyType_GenericNew(Del_type, NULL, NULL); etc

/* call frozenset() to get the empty frozenset singleton */

Objects/unicodeobject.c:1803:unicode_is_singleton(PyObject *unicode)

Objects/bytesobject.c:92: /* empty byte string singleton */

Objects/codeobject.c:504: /* Py_None and Py_Ellipsis are singletons. */

Objects/codeobject.c:541: /* use True, False and None singleton as tags for the real and imag

Objects/setobject.c:1063:/* The empty frozenset is a singleton */

Include/datetime.h:158: /* singletons */

Doc/faq/programming.rst:283:Note that using a module is also the basis for implementing the Singleton design

Doc/reference/datamodel.rst:310: pair: singleton; tuple

Doc/c-api/module.rst:258:singletons: if the *sys.modules* entry is removed and the module is re-imported,

Doc/c-api/module.rst:452:Single-phase initialization creates singleton modules that can be looked up

Doc/library/turtle.rst:63: The function :func:`Screen` returns a singleton object of a

Doc/library/stdtypes.rst:4646:``None`` (a built-in name). ``type(None)()`` produces the same singleton.

Doc/library/stdtypes.rst:4673:``type(NotImplemented)()`` produces the singleton instance.

Doc/library/enum.rst:1026:The most interesting thing about Enum members is that they are singletons.

Doc/library/unittest.mock.rst:549: mock and unless the function returns the :data:`DEFAULT` singleton the

Doc/library/marshal.rst:46:singletons :const:`None`, :const:`Ellipsis` and :exc:`StopIteration` can also be

Doc/whatsnew/3.6.rst:2405:The ``PyExc_RecursionErrorInst`` singleton that was part of the public API