Correct use of try,except and raise?

[Roy Smith]

ssecorp <circularfunc at gmail.com> wrote:

> i dont get what you mean, if i dont do anything python will raise an
> indexerror so it is an indexerror.

You wrote:

> > >     def pop(self):
> > >         try:
> > >             return self.queue.pop(0)
> > >         except:
> > >             raise IndexError, "pop from empty queue"

You are assuming that the only possible exception that can be thrown by 
"return self.queue.pop(0)" is IndexError.  Maybe, maybe not.  I gave you 
one example of how something else could be thrown -- a typo in your code 
leading to a NameError.  Maybe even something more exotic like MemoryError?

The defensive thing to do is catch exactly the exception you expect to 
happen.  In this case, that means IndexError.