Typo fix

pep-3116.txt

@@ -252,7 +252,7 @@ forces all cached write data to be written to the underlying
 future reads are forced to go back to the disk).
 
 *Q: Do we want to mandate in the specification that switching between
-reading to writing on a read-write object implies a .flush()?  Or is
+reading and writing on a read-write object implies a .flush()?  Or is
 that an implementation convenience that users should not rely on?*
 
 For a read-only ``BufferedRandom`` object, ``.writable()`` returns