Clarify description of update() (Boyd Roberts)

Clarify description of new (Tim Peters)

pep-0247.txt

@@ -26,15 +26,17 @@ Specification
     new([string])
     new([key] , [string])
 
-        Create a new hashing object and return it.  You can now feed
-        arbitrary strings into the object using its update() method,
-        and can ask for the hash value at any time by calling its
-        digest() method.
-
-        The 'string' parameter, if supplied, will be immediately
-        hashed into the object's starting state; an empty string or
-        None.  For keyed hashes such as HMAC, 'key' is a string
-        containing the starting key.  
+        Create a new hashing object and return it.  The first form is
+        for hashes that are unkeyed; most hashes such as MD5 or SHA
+        are unkeyed.  For keyed hashes such as HMAC, 'key' is a string
+        containing the starting key.  The 'string' parameter, if
+        supplied, will be immediately hashed into the object's
+        starting state, as if obj.update(string) was called.
+        
+        After creating a hashing object, arbitrary strings can be fed
+        into the object using its update() method, and the hash value
+        can be obtained at any time by calling the object's digest()
+        method.
 
         Arbitrary additional keyword arguments can be added to this
         function, but if they're not supplied, sensible default values
@@ -88,9 +90,11 @@ Specification
         for the digits 'a' through 'f'.  Like the .digest() method, this
         method mustn't alter the object.
         
-    update(arg)
+    update(string)
 
-        Update this hashing object with the string 'arg'.
+        Hash 'string' into the current state of the hashing object.
+        update() can be called any number of times during a hashing
+        object's lifetime.
 
     Hashing modules can define additional module-level functions or 
     object methods and still be compliant with this specification.