bpo-36144: Document PEP 584 (pythonGH-18659)

Author: brandtbucher

Doc/library/stdtypes.rst

@@ -4392,6 +4392,22 @@ pairs within braces, for example: ``{'jack': 4098, 'sjoerd': 4127}`` or ``{4098:
          >>> d.values() == d.values()
          False
 
+   .. describe:: d | other
+
+      Create a new dictionary with the merged keys and values of *d* and
+      *other*, which must both be dictionaries. The values of *other* take
+      priority when *d* and *other* share keys.
+
+      .. versionadded:: 3.9
+
+   .. describe:: d |= other
+
+      Update the dictionary *d* with keys and values from *other*, which may be
+      either a :term:`mapping` or an :term:`iterable` of key/value pairs. The
+      values of *other* take priority when *d* and *other* share keys.
+
+      .. versionadded:: 3.9
+
    Dictionaries compare equal if and only if they have the same ``(key,
    value)`` pairs (regardless of ordering). Order comparisons ('<', '<=', '>=', '>') raise
    :exc:`TypeError`.

Doc/whatsnew/3.9.rst

@@ -70,6 +70,12 @@ Summary -- Release highlights
 New Features
 ============
 
+Dictionary Merge & Update Operators
+-----------------------------------
+
+Merge (``|``) and update (``|=``) operators have been added to the built-in
+:class:`dict` class.  See :pep:`584` for a full description.
+(Contributed by Brandt Bucher in :issue:`36144`.)
 
 
 Other Language Changes