Initial implementation.

Author: ericvsmith

Doc/builtins/stdtypes.rst

@@ -3236,12 +3236,21 @@ brackets (``{}``).
 Each replacement field must contain an expression, optionally followed by:
 
 * a *debug specifier* -- an equal sign (``=``);
-* a *conversion specifier* -- ``!s``, ``!r`` or ``!a``; and/or
+* a *conversion specifier* -- ``!s``, ``!r``, ``!a`` or ``!p``; and/or
 * a *format specifier* prefixed with a colon (``:``).
 
 See the :ref:`Lexical Analysis section on f-strings <f-strings>` for details
 on the syntax of these fields.
 
+The ``!p`` conversion calls :c:func:`PyObject_Pretty`. Its format specifier is
+passed as the ``printer`` argument without converting a replacement field to a
+string. The format specifier must be a single replacement field whose value is
+callable. If it is omitted or empty, ``NULL`` is passed as the printer argument
+to :c:func:`PyObject_Pretty`, which uses a default printer that calls
+``__pprint__()`` when available and interprets its iterable as a description
+of the object's layout and contents. If the method is absent, the default
+printer falls back to :func:`repr`.
+
 Debug specifier
 ^^^^^^^^^^^^^^^
 

Doc/c-api/object.rst

@@ -397,6 +397,15 @@ Object Protocol
       This function now includes a debug assertion to help ensure that it
       does not silently discard an active exception.
 
+.. c:function:: PyObject* PyObject_Pretty(PyObject *o, PyObject *printer)
+
+   Return the result of calling *printer* with *o*. If *printer* is ``NULL``,
+   a default printer is created, called with *o*, and discarded. The default
+   printer is implemented in the :mod:`_pprint` module. It calls *o*'s
+   ``__pprint__()`` method if present and interprets the returned stream as a
+   description of the object's layout and contents. If the method is absent,
+   the default printer returns the result of :c:func:`PyObject_Repr`.
+
 
 .. c:function:: PyObject* PyObject_Bytes(PyObject *o)
 

Doc/data/refcounts.dat

@@ -1916,6 +1916,10 @@ PyObject_Size:PyObject*:o:0:
 PyObject_Str:PyObject*::+1:
 PyObject_Str:PyObject*:o:0:
 
+PyObject_Pretty:PyObject*::+1:
+PyObject_Pretty:PyObject*:o:0:
+PyObject_Pretty:PyObject*:printer:0:
+
 Py_TYPE:PyObject*::0:
 Py_TYPE:PyObject*:ob:0:
 

Doc/data/stable_abi.dat

@@ -1145,7 +1145,7 @@ After the expression, replacement fields may optionally contain:
 
 * a *debug specifier* -- an equal sign (``=``), optionally surrounded by
   whitespace on one or both sides;
-* a *conversion specifier* -- ``!s``, ``!r`` or ``!a``; and/or
+* a *conversion specifier* -- ``!s``, ``!r``, ``!a`` or ``!p``; and/or
 * a *format specifier* prefixed with a colon (``:``).
 
 See the :ref:`Standard Library section on f-strings <stdtypes-fstrings>`

Doc/reference/lexical_analysis.rst

@@ -128,6 +128,7 @@ PyAPI_FUNC(void) PyEval_ReleaseThread(PyThreadState *tstate);
 #define FVC_STR       0x1
 #define FVC_REPR      0x2
 #define FVC_ASCII     0x3
+#define FVC_PRETTY    0x4
 #define FVS_MASK      0x4
 #define FVS_HAVE_SPEC 0x4
 

Include/ceval.h

@@ -205,6 +205,7 @@ struct _Py_global_strings {
         STRUCT_FOR_ID(__path__)
         STRUCT_FOR_ID(__pos__)
         STRUCT_FOR_ID(__pow__)
+        STRUCT_FOR_ID(__pprint__)
         STRUCT_FOR_ID(__prepare__)
         STRUCT_FOR_ID(__qualname__)
         STRUCT_FOR_ID(__radd__)

Include/internal/pycore_global_objects_fini_generated.h

@@ -304,6 +304,7 @@ Known values:
     Python 3.16a1 3704 (Replace DELETE_ATTR with PUSH_NULL; STORE_ATTR)
     Python 3.16a1 3705 (Add INTRINSIC_ADD_CONDITIONAL_ANNOTATION)
     Python 3.16a1 3706 (Add INTRINSIC_MATCH_CLASS_ISINSTANCE)
+    Python 3.16a1 3707 (Add FORMAT_PRETTY opcode)
 
     Python 3.17 will start with 3750
 
@@ -313,7 +314,7 @@ Known values:
 
 */
 
-#define PYC_MAGIC_NUMBER 3706
+#define PYC_MAGIC_NUMBER 3707
 /* This is equivalent to converting PYC_MAGIC_NUMBER to 2 bytes
    (little-endian) and then appending b'\r\n'. */
 #define PYC_MAGIC_NUMBER_TOKEN \