[Tutor] Two Questions...(i) Checking for None (ii) Making commandline arguments mutually exclusive

[Dustin J. Mitchell]

> if x == None
> 
> As simple as that.

In fact, I think the following is even a little more readable:

  if x is None

and in fact that syntax has some advantages in various corner cases.  It's
largely a matter of preference.

Dustin