Add _repr method to named tuples

Author: bswck

Doc/library/collections.rst

@@ -849,8 +849,9 @@ they add the ability to access fields by name instead of position index.
     Returns a new tuple subclass named *typename*.  The new subclass is used to
     create tuple-like objects that have fields accessible by attribute lookup as
     well as being indexable and iterable.  Instances of the subclass also have a
-    helpful docstring (with typename and field_names) and a helpful :meth:`__repr__`
-    method which lists the tuple contents in a ``name=value`` format.
+    helpful docstring (with typename and field_names) and a helpful :meth:`_repr`
+    method, backing the default :meth:`__repr__`, which lists the tuple contents
+    in a ``name=value`` format.
 
     The *field_names* are a sequence of strings such as ``['x', 'y']``.
     Alternatively, *field_names* can be a single string with each fieldname
@@ -967,6 +968,21 @@ field names, the method and attribute names start with an underscore.
         remediation is to cast the result to the desired type:
         ``OrderedDict(nt._asdict())``.
 
+.. method:: somenamedtuple._repr()
+
+    Return a representation of the named tuple contents in a ``name=value`` format.
+    The default ``__repr__`` implementation uses it to produce the representation.
+
+    .. doctest::
+
+        >>> p = Point(x=11, y=22)
+        >>> p._repr()
+        'Point(x=11, y=22)'
+        >>> p
+        Point(x=11, y=22)
+
+    .. versionadded:: 3.14
+
 .. method:: somenamedtuple._replace(**kwargs)
 
     Return a new instance of the named tuple replacing specified fields with new
@@ -1064,6 +1080,9 @@ fields:
 .. versionchanged:: 3.5
    Property docstrings became writeable.
 
+.. versionchanged:: 3.13
+   Default :func:`_repr`
+
 .. seealso::
 
    * See :class:`typing.NamedTuple` for a way to add type hints for named

Doc/library/typing.rst

@@ -2344,6 +2344,17 @@ types.
    Calls to :func:`super` are supported inside user-defined methods of ``NamedTuple`` subclasses
    to reuse functionality from built-in classes :class:`tuple` and :class:`object`.
 
+   To allow extending named tuple's default ``__repr__``, it can be as well accessed with ``self._repr``,
+   as ``super().__repr__`` in a ``NamedTuple`` subclass resolves to :meth:`tuple.__repr__`:
+
+      class Import(NamedTuple):
+          target: str
+
+          def __repr__(self) -> str:
+              # super().__repr__() -> ('target',)
+              # self._repr() -> Import(target='target')
+              return f'<Token {self._repr()}>'  # <Token Import(target='target')>
+
    ``NamedTuple`` subclasses can be generic::
 
       class Group[T](NamedTuple):

Lib/collections/__init__.py

@@ -469,10 +469,15 @@ def _replace(self, /, **kwds):
     _replace.__doc__ = (f'Return a new {typename} object replacing specified '
                         'fields with new values')
 
-    def __repr__(self):
+    def _repr(self):
         'Return a nicely formatted representation string'
         return self.__class__.__name__ + repr_fmt % self
 
+    def __repr__(self):
+        return self._repr()
+
+    __repr__.__doc__ = _repr.__doc__
+
     def _asdict(self):
         'Return a new dict which maps field names to their values.'
         return _dict(_zip(self._fields, self))
@@ -486,6 +491,7 @@ def __getnewargs__(self):
         __new__,
         _make.__func__,
         _replace,
+        _repr,
         __repr__,
         _asdict,
         __getnewargs__,
@@ -503,6 +509,7 @@ def __getnewargs__(self):
         '_make': _make,
         '__replace__': _replace,
         '_replace': _replace,
+        '_repr': _repr,
         '__repr__': __repr__,
         '_asdict': _asdict,
         '__getnewargs__': __getnewargs__,

Lib/test/test_collections.py

@@ -648,10 +648,12 @@ def test_name_conflicts(self):
     def test_repr(self):
         A = namedtuple('A', 'x')
         self.assertEqual(repr(A(1)), 'A(x=1)')
+        self.assertEqual(A(2)._repr(), 'A(x=2)')
         # repr should show the name of the subclass
         class B(A):
             pass
         self.assertEqual(repr(B(1)), 'B(x=1)')
+        self.assertEqual(B(2)._repr(), 'B(x=2)')
 
     def test_keyword_only_arguments(self):
         # See issue 25628

Lib/test/test_typing.py

@@ -8154,6 +8154,24 @@ def count(self, item):
         self.assertEqual(aspiring_triager.count("Bartosz"), 1)
         self.assertEqual(aspiring_triager.count("Peter"), -1)  # already a triager!
 
+    def test_overridden_repr(self):
+        class CustomRepresentation(NamedTuple):
+            namedtuple_style: bool
+
+            def __repr__(self):
+                if self.namedtuple_style:
+                    return f"<namedtuple style {self._repr()}>"
+                return f"<tuple style {super().__repr__()}>"
+
+        namedtuple_style_repr = CustomRepresentation(namedtuple_style=True)
+        self.assertEqual(
+            repr(namedtuple_style_repr),
+            "<namedtuple style CustomRepresentation(namedtuple_style=True)>"
+        )
+
+        tuple_style_repr = CustomRepresentation(namedtuple_style=False)
+        self.assertEqual(repr(tuple_style_repr), "<tuple style (False,)>")
+
     def test_namedtuple_keyword_usage(self):
         with self.assertWarnsRegex(
             DeprecationWarning,

Lib/typing.py

@@ -2953,7 +2953,7 @@ def annotate(format):
 # attributes prohibited to set in NamedTuple class syntax
 _prohibited = frozenset({'__new__', '__init__', '__slots__', '__getnewargs__',
                          '_fields', '_field_defaults',
-                         '_make', '_replace', '_asdict', '_source'})
+                         '_make', '_replace', '_repr', '_asdict', '_source'})
 
 _special = frozenset({'__module__', '__name__', '__annotations__', '__annotate__'})