How to know more about an exception?

[Timmy]

Hi, 
   I has a question about exception in python.
   I know that an exception can be re-raised. 
Is there any simple way provided by python itself that I can know the current exception is 
just firstly occurred or it is re-raised by previous exception?
I need to know whether the exception is firstly occurred or not because I want to just display an error message if it's
firstly occur and skip display error message if it is just re-raised by previous exception.

Thanks!