set_dialect is the wrong name. It conveys the notion of a single dialect.

register_dialect is better.

pep-0305.txt

@@ -169,14 +169,14 @@ follows::
 
 Three functions are defined in the API to set, get and list dialects::
 
-    set_dialect(name, dialect)
+    register_dialect(name, dialect)
     dialect = get_dialect(name)
     known_dialects = list_dialects()
 
 The dialect parameter is a class or instance whose attributes are the
 formatting parameters defined in the next section.  The
 list_dialects() function returns all the registered dialect names as
-given in previous set_dialect() calls (both predefined and
+given in previous register_dialect() calls (both predefined and
 user-defined).
 
 
@@ -186,7 +186,7 @@ Formatting Parameters
 Both the reader and writer constructors take several specific
 formatting parameters, specified as keyword parameters.  The
 parameters are also the keys for the input and output mapping objects
-for the set_dialect() and get_dialect() module functions.
+for the register_dialect() and get_dialect() module functions.
 
 - ``quotechar`` specifies a one-character string to use as the quoting
   character.  It defaults to '"'.  Setting this to None has the same