gistfile1.txt

 cpython gh-117348/import-perf @ ./python.exe -X importtime -c 'import configparser' 2>1 | grep -E '(cumul|configparser)'
import time: self [us] | cumulative | imported package
import time:      7573 |      15790 | configparser
 cpython gh-117348/import-perf @ ./python.exe -X importtime -c 'import configparser' 2>1 | grep -E '(cumul|configparser)'
import time: self [us] | cumulative | imported package
import time:      1760 |      10852 | configparser
 cpython gh-117348/import-perf @ git stash pop
On branch gh-117348/import-perf
Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git restore <file>..." to discard changes in working directory)
        modified:   Lib/configparser.py

no changes added to commit (use "git add" and/or "git commit -a")
Dropped refs/stash@{0} (8dfe3a6662fbbadd31733799362a11ee667ba474)
 cpython gh-117348/import-perf @ git diff
diff --git a/Lib/configparser.py b/Lib/configparser.py
index ca9fef532b..91e2b9299a 100644
--- a/Lib/configparser.py
+++ b/Lib/configparser.py
@@ -146,13 +146,13 @@
 from collections.abc import Iterable, MutableMapping
 from collections import ChainMap as _ChainMap
 import contextlib
-from dataclasses import dataclass, field
 import functools
 import io
 import itertools
 import os
 import re
 import sys
+import types
 
 __all__ = ("NoSectionError", "DuplicateOptionError", "DuplicateSectionError",
            "NoOptionError", "InterpolationError", "InterpolationDepthError",
@@ -537,19 +537,21 @@ def _interpolate_some(self, parser, option, accum, rest, section, map,
                     "found: %r" % (rest,))
 
 
-@dataclass
-class _ReadState:
-    elements_added : set[str] = field(default_factory=set)
+class _ReadState(types.SimpleNamespace):
+    elements_added : set[str]
     cursect : dict[str, str] | None = None
     sectname : str | None = None
     optname : str | None = None
     lineno : int = 0
     indent_level : int = 0
-    errors : list[ParsingError] = field(default_factory=list)
+    errors : list[ParsingError]
 
+    def __init__(self):
+        self.elements_added = set()
+        self.errors = list()
 
-@dataclass
-class _Prefixes:
+
+class _Prefixes(types.SimpleNamespace):
     full : Iterable[str]
     inline : Iterable[str]
 
 cpython gh-117348/import-perf @ ./python.exe -X importtime -c 'import configparser' 2>1 | grep -E '(cumul|configparser)'
import time: self [us] | cumulative | imported package
import time:      6934 |      10799 | configparser
 cpython gh-117348/import-perf @ ./python.exe -X importtime -c 'import configparser' 2>1 | grep -E '(cumul|configparser)'
import time: self [us] | cumulative | imported package
import time:       967 |       4339 | configparser