PEP 572: Add another alternate spelling

pep-0572.rst

@@ -163,6 +163,10 @@ These list comprehensions are all approximately equivalent::
             yield [y, x/y]
     stuff = list(g())
 
+    # Using a mutable cache object (various forms possible)
+    c = {}
+    stuff = [[c.update(y=f(x)) or c['y'], x/c['y']] for x in range(5)]
+
     # Using a statement-local name
     stuff = [[(f(x) as y), x/y] for x in range(5)]