diff --git a/Lib/string.py b/Lib/string.py
index a7261a9150..b423ff5dc6 100644
--- a/Lib/string.py
+++ b/Lib/string.py
@@ -52,13 +52,15 @@ def capwords(s, sep=None):
 import re as _re
 from collections import ChainMap as _ChainMap
 
+_sentinel_dict = {}
+
 class _TemplateMetaclass(type):
     pattern = r"""
     %(delim)s(?:
       (?P<escaped>%(delim)s) |   # Escape sequence of two delimiters
       (?P<named>%(id)s)      |   # delimiter and a Python identifier
-      \{(?P<braced>%(bid)s)\}  #|   # delimiter and a braced identifier
-    #   (?P<invalid>)              # Other ill-formed delimiter exprs
+      {(?P<braced>%(bid)s)}  |   # delimiter and a braced identifier
+      (?P<invalid>)              # Other ill-formed delimiter exprs
     )
     """
 
@@ -83,7 +85,7 @@ class Template(metaclass=_TemplateMetaclass):
     # without the ASCII flag.  We can't add re.ASCII to flags because of
     # backward compatibility.  So we use the ?a local flag and [a-z] pattern.
     # See https://bugs.python.org/issue31672
-    idpattern = r'([_a-z][_a-z0-9]*)'
+    idpattern = r'(?a:[_a-z][_a-z0-9]*)'
     braceidpattern = None
     flags = _re.IGNORECASE
 
@@ -104,19 +106,11 @@ class Template(metaclass=_TemplateMetaclass):
         raise ValueError('Invalid placeholder in string: line %d, col %d' %
                          (lineno, colno))
 
-    def substitute(*args, **kws):
-        if not args:
-            raise TypeError("descriptor 'substitute' of 'Template' object "
-                            "needs an argument")
-        self, *args = args  # allow the "self" keyword be passed
-        if len(args) > 1:
-            raise TypeError('Too many positional arguments')
-        if not args:
+    def substitute(self, mapping=_sentinel_dict, /, **kws):
+        if mapping is _sentinel_dict:
             mapping = kws
         elif kws:
-            mapping = _ChainMap(kws, args[0])
-        else:
-            mapping = args[0]
+            mapping = _ChainMap(kws, mapping)
         # Helper function for .sub()
         def convert(mo):
             # Check the most common path first.
@@ -131,19 +125,11 @@ class Template(metaclass=_TemplateMetaclass):
                              self.pattern)
         return self.pattern.sub(convert, self.template)
 
-    def safe_substitute(*args, **kws):
-        if not args:
-            raise TypeError("descriptor 'safe_substitute' of 'Template' object "
-                            "needs an argument")
-        self, *args = args  # allow the "self" keyword be passed
-        if len(args) > 1:
-            raise TypeError('Too many positional arguments')
-        if not args:
+    def safe_substitute(self, mapping=_sentinel_dict, /, **kws):
+        if mapping is _sentinel_dict:
             mapping = kws
         elif kws:
-            mapping = _ChainMap(kws, args[0])
-        else:
-            mapping = args[0]
+            mapping = _ChainMap(kws, mapping)
         # Helper function for .sub()
         def convert(mo):
             named = mo.group('named') or mo.group('braced')
@@ -173,16 +159,7 @@ class Template(metaclass=_TemplateMetaclass):
 # The field name parser is implemented in _string.formatter_field_name_split
 
 class Formatter:
-    def format(*args, **kwargs):
-        if not args:
-            raise TypeError("descriptor 'format' of 'Formatter' object "
-                            "needs an argument")
-        self, *args = args  # allow the "self" keyword be passed
-        try:
-            format_string, *args = args # allow the "format_string" keyword be passed
-        except ValueError:
-            raise TypeError("format() missing 1 required positional "
-                            "argument: 'format_string'") from None
+    def format(self, format_string, /, *args, **kwargs):
         return self.vformat(format_string, args, kwargs)
 
     def vformat(self, format_string, args, kwargs):