gh-102578: Optimise setting and deleting mutable attributes on non-dataclass subclasses of frozen dataclasses

Lib/dataclasses.py

@@ -617,10 +617,10 @@ def _frozen_get_del_attr(cls, fields, globals):
     locals = {'cls': cls,
               'FrozenInstanceError': FrozenInstanceError}
     if fields:
-        fields_str = '(' + ','.join(repr(f.name) for f in fields) + ',)'
+        fields_str = '{' + ','.join(repr(f.name) for f in fields) + '}'
     else:
-        # Special case for the zero-length tuple.
-        fields_str = '()'
+        # Special case for the zero-length set.
+        fields_str = 'set()'
     return (_create_fn('__setattr__',
                       ('self', 'name', 'value'),
                       (f'if type(self) is cls or name in {fields_str}:',

Misc/NEWS.d/next/Library/2023-03-10-10-10-00.gh-issue-102573.GQ7sV6.rst

@@ -0,0 +1 @@
+Use ``set``-based name lookup rather than ``tuple``\s for frozen dataclasses