Add some information to the input section

Change variable name: entered -> user_input
Add some information to the section and reflow text.

doc/Language/py-nutshell.pod6

@@ -15,7 +15,7 @@ constructs and idioms.
 
 Let's start with printing "Hello, world!". L<put> in Perl 6 is the
 equivalent of L<print> in Python.  Like Python 2, parentheses are
-optional.  A return is added to the end of the line.
+optional. A return is added to the end of the line.
 
 Python 2
 
@@ -728,17 +728,21 @@ run on entering or leaving a block.
 
 =head2 X<C<input>|Python>
 
-In Python 3, the C<input> keyword is used to prompt the user:
+In Python 3, the C<input> keyword is used to prompt the user. C<input> can be
+provided with an optional argument which is written to standard output without
+a trailing newline:
 
 =begin code :lang<python>
-entered = input("Say hi → ")
-print(entered)
+user_input = input("Say hi → ")
+print(user_input)
 =end code
 
-When prompted, you can enter C<Hi> or any other string, which will be stored in the C<entered> variable. This is similar to L<prompt> in Perl 6:
 
-    my $entered = prompt(" Say hi → ");
-    say $entered # OUTPUT: whatever you entered.
+When prompted, you can enter C<Hi> or any other string, which will be stored 
+in the C<user_input> variable. This is similar to L<prompt> in Perl 6:
+
+    my $user_input = prompt("Say hi → ");
+    say $user_input; # OUTPUT: whatever you entered.
 
 =end pod