Subclassing PrettyPrinter.format doesn't work in all cases

Bug report

Bug description:

See also the earlier fixed https://github.com/python/cpython/issues/73036. This appears to have only been a partial fix, or it has regressed.

import collections
import pprint
import types


SENTINAL = object()


class _hashable:
    def __hash__(self):
        return 1


HASHABLE_SENTINAL = _hashable()


class CustomPrettyPrinter(pprint.PrettyPrinter):
    def format(self, obj, context, maxlevels, level):
        if obj is SENTINAL:
            return "SENTINAL", True, False
        elif obj is HASHABLE_SENTINAL:
            return "HASHABLE_SENTINAL", True, False
        else:
            return super().format(obj, context, maxlevels, level)


if __name__ == "__main__":
    printer = CustomPrettyPrinter(sort_dicts=False)

    test_data = {
        "item": SENTINAL,
        "dict": {"a": SENTINAL},
        "dict_key": {HASHABLE_SENTINAL: 1},
        "OrderedDict": collections.OrderedDict({"a": SENTINAL}),
        "OrderedDict_key": collections.OrderedDict({HASHABLE_SENTINAL: 1}),
        "list": [SENTINAL],
        "tuple": (SENTINAL,),
        "set": {SENTINAL},
        "frozenset": frozenset({SENTINAL}),
        "mappingproxy": types.MappingProxyType({"a": SENTINAL}),
        "mappingproxy_key": types.MappingProxyType({HASHABLE_SENTINAL: 1}),
        "SimpleNamespace": types.SimpleNamespace(a=SENTINAL),
        "defaultdict": collections.defaultdict(list, {"a": SENTINAL}),
        "defaultdict_key": collections.defaultdict(list, {HASHABLE_SENTINAL: 1}),
        "Counter": collections.Counter({"a": SENTINAL}),
        "Counter_key": collections.Counter({HASHABLE_SENTINAL: 1}),
        "deque": collections.deque([SENTINAL]),
    }

    printer.pprint(test_data)

This outputs:

{'item': SENTINAL,
 'dict': {'a': SENTINAL},
 'dict_key': {HASHABLE_SENTINAL: 1},
 'OrderedDict': OrderedDict({'a': <object object at 0x1041f4660>}),
 'OrderedDict_key': OrderedDict([(HASHABLE_SENTINAL, 1)]),
 'list': [SENTINAL],
 'tuple': (SENTINAL,),
 'set': {<object object at 0x1041f4660>},
 'frozenset': frozenset({<object object at 0x1041f4660>}),
 'mappingproxy': mappingproxy({'a': <object object at 0x1041f4660>}),
 'mappingproxy_key': mappingproxy({HASHABLE_SENTINAL: 1}),
 'SimpleNamespace': namespace(a=<object object at 0x1041f4660>),
 'defaultdict': defaultdict(<class 'list'>,
                            {'a': SENTINAL}),
 'defaultdict_key': defaultdict(<class 'list'>,
                                {HASHABLE_SENTINAL: 1}),
 'Counter': Counter({'a': <object object at 0x1041f4660>}),
 'Counter_key': Counter({<__main__._hashable object at 0x1045e4d70>: 1}),
 'deque': deque([<object object at 0x1041f4660>])}

Every instance of < in that output is a bug.

CPython versions tested on:

3.13

Operating systems tested on:

macOS

Linked PRs

• gh-133238

Beginne damit, den Reproducer auszuführen und pprint.PrettyPrinter.format zu untersuchen, insbesondere wie es die aufgeführten Containertypen und deren Inhalte behandelt. Vergleiche jede Ausgabe mit der erwarteten benutzerdefinierten Formatierung und füge anschließend Regressionstests für die Fälle hinzu, in denen der Override umgangen wird. Die Aufgabe ist abgeschlossen, wenn jedes im Reproducer gezeigte oder repr die format-Methode der Subklasse berücksichtigt.