gh-152334: Add curses key-management functions

Add define_key(), key_defined() and keyok(), the ncurses extensions for
managing how control strings are recognized as key codes, beyond the
predefined terminfo keys and the all-or-nothing window.keypad().

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: serhiy-storchaka

Doc/library/curses.rst

@@ -345,6 +345,37 @@ The module :mod:`!curses` defines the following functions:
    a key with that value.
 
 
+.. function:: define_key(definition, keycode)
+
+   Define an escape sequence *definition*, a string, as a key that generates
+   the key code *keycode*, so that :mod:`curses` interprets it like one of the
+   keys predefined in the terminal database.
+
+   If *definition* is ``None``, any existing binding for *keycode* is removed.
+   If *keycode* is zero or negative, any existing binding for *definition* is
+   removed.
+
+   .. versionadded:: next
+
+
+.. function:: key_defined(definition)
+
+   Return the key code bound to the escape sequence *definition*, a string,
+   ``0`` if no key code is bound to it, or ``-1`` if *definition* is a prefix
+   of a longer bound sequence (and so is ambiguous).
+
+   .. versionadded:: next
+
+
+.. function:: keyok(keycode, enable)
+
+   Enable (if *enable* is true) or disable (otherwise) interpretation of the
+   key code *keycode*.  Unlike :meth:`window.keypad`, this affects a single
+   key code rather than all of them.
+
+   .. versionadded:: next
+
+
 .. function:: halfdelay(tenths)
 
    Used for half-delay mode, which is similar to cbreak mode in that characters

Doc/whatsnew/3.16.rst

@@ -165,6 +165,11 @@ curses
   :func:`~curses.scr_set`, which dump the whole screen to a file and restore it.
   (Contributed by Serhiy Storchaka in :gh:`152260`.)
 
+* Add the :mod:`curses` key-management functions :func:`~curses.define_key`,
+  :func:`~curses.key_defined` and :func:`~curses.keyok`, available when built
+  against an ncurses with ``NCURSES_EXT_FUNCS``.
+  (Contributed by Serhiy Storchaka in :gh:`152334`.)
+
 gzip
 ----
 

Lib/test/test_curses.py

@@ -1315,6 +1315,21 @@ def test_env_queries(self):
                 self.assertIsInstance(c, str)
                 self.assertEqual(len(c), 1)
 
+    @requires_curses_func('define_key')
+    def test_key_management(self):
+        # Bind a custom escape sequence to a free key code and read it back.
+        seq = '\x1bspam'
+        keycode = 0o600
+        curses.define_key(seq, keycode)
+        self.assertEqual(curses.key_defined(seq), keycode)
+        # keyok enables or disables interpretation of a single key code.
+        # Use the key code just defined, which is guaranteed to be known.
+        self.assertIsNone(curses.keyok(keycode, False))
+        self.assertIsNone(curses.keyok(keycode, True))
+        # Passing None removes the binding for the key code.
+        curses.define_key(None, keycode)
+        self.assertEqual(curses.key_defined(seq), 0)
+
     def test_output_options(self):
         stdscr = self.stdscr
 

Misc/NEWS.d/next/Library/2026-06-26-22-50-00.gh-issue-152334.Mt7vQx.rst

@@ -0,0 +1,2 @@
+Add the :func:`curses.define_key`, :func:`curses.key_defined` and
+:func:`curses.keyok` key-management functions.

Modules/_cursesmodule.c

@@ -5776,6 +5776,77 @@ _curses_has_key_impl(PyObject *module, int key)
 }
 #endif
 
+#if defined(NCURSES_EXT_FUNCS) && NCURSES_EXT_FUNCS
+/*[clinic input]
+_curses.define_key
+
+    definition: str(accept={str, NoneType})
+        Escape sequence to bind, or None to remove a binding.
+    keycode: int
+        Key code to generate.
+    /
+
+Define an escape sequence for a key code.
+
+If definition is None, any existing binding for keycode is removed.
+If keycode is zero or negative, the binding for definition is removed.
+[clinic start generated code]*/
+
+static PyObject *
+_curses_define_key_impl(PyObject *module, const char *definition,
+                        int keycode)
+/*[clinic end generated code: output=9dc655653bb09062 input=8db9e0d8802c709f]*/
+{
+    PyCursesStatefulInitialised(module);
+
+    return curses_check_err(module, define_key(definition, keycode),
+                            "define_key", NULL);
+}
+
+/*[clinic input]
+_curses.key_defined
+
+    definition: str
+        Escape sequence.
+    /
+
+Return the key code bound to an escape sequence.
+
+Return 0 if no key code is bound to the escape sequence, or -1 if the
+escape sequence is a prefix of another bound sequence (so ambiguous).
+[clinic start generated code]*/
+
+static PyObject *
+_curses_key_defined_impl(PyObject *module, const char *definition)
+/*[clinic end generated code: output=2d357e01fe277c88 input=03749d7bd79d8d2c]*/
+{
+    PyCursesStatefulInitialised(module);
+
+    return PyLong_FromLong(key_defined(definition));
+}
+
+/*[clinic input]
+_curses.keyok
+
+    keycode: int
+        Key code.
+    enable: bool
+        Whether the key code is interpreted.
+    /
+
+Enable or disable interpretation of an individual key code.
+[clinic start generated code]*/
+
+static PyObject *
+_curses_keyok_impl(PyObject *module, int keycode, int enable)
+/*[clinic end generated code: output=43eab0b4d9973e44 input=5bee51d850f481b9]*/
+{
+    PyCursesStatefulInitialised(module);
+
+    return curses_check_err(module, keyok(keycode, enable), "keyok", NULL);
+}
+#endif
+
 /*[clinic input]
 _curses.init_color
 
@@ -7759,6 +7830,9 @@ static PyMethodDef cursesmodule_methods[] = {
     _CURSES_HAS_IC_METHODDEF
     _CURSES_HAS_IL_METHODDEF
     _CURSES_HAS_KEY_METHODDEF
+    _CURSES_DEFINE_KEY_METHODDEF
+    _CURSES_KEY_DEFINED_METHODDEF
+    _CURSES_KEYOK_METHODDEF
     _CURSES_HALFDELAY_METHODDEF
     _CURSES_INIT_COLOR_METHODDEF
     _CURSES_INIT_PAIR_METHODDEF