How to return an "not string' error in function?

[Cameron Laird]

In article <1158848968.493858.96600 at k70g2000cwa.googlegroups.com>,
 <breakfastea at gmail.com> wrote:
>Thank you so much it answers my humble question perfectly:)
>

HOWEVER, to answer you final question, yes, there is a different
and, in general, better, way.  While there's a lot to say about
good Python style and typing, I'll summarize at a high level:
you shouldn't have to check types.  I can understand that you
are working to make a particular function particularly robust, 
and are trying to account for a wide range of inputs.  This is
healthy.  In stylish Python, though, you generally don't need
type checking.  How would it be, for example, if someone passed
the number 3 to your function.  Is that an error?  Do you want
it automatically interpreted as the string "3"?  You can achieve
these results withOUT a sequence of

  if isinstance(...
  elif isinstance(...
  ...

perhaps with something as simple as

  my_input = str(my_input).

One of us will probably follow-up with a reference to a more
detailed write-up of the subject.