[Python-ideas] syntax to continue into the next subsequent except block

[Terry Reedy]

On 9/13/2012 5:05 PM, Paul Wiseman wrote:
> I think it would be useful if there was a way to skip into the next
> except block, perhaps with continue as I think it's currently always
> illegal to use in an except block. I don't believe there's currently a
> way to do this.
>
> This is my reasoning, often there's multiple reasons for exceptions that
> raise the same exception, as an example an IOError might get raised for
> lots of different reasons. If you want to handle one or several of these
> reasons, you have to catch all exceptions of this type, but there's not
> really a way to "put back" the exception if it isn't the type you were
> after. For instance
>
> try:
>      operation()
> except IOError as err:
>      if err.errno == 2:
>          do_something()
>      else:
>          continue #This would continue the except down to the next
> check, except Exception
> except Exception as err:
>      logger.error("Error performing operation: {}".format(err.message)")
>      some_clean_up()
>      raise

> The current alternatives to get this behaviour I don't believe are as
> nice, but maybe I'm missing something

As you already know, raise puts the exception back, in a sense

try:
   try:
     operation()
   except IOError as err:
     if err.errno == 2:
        do_something()
     else:
       raise
except Exception as err:
      logger.error("Error performing operation: {}".format(err.message)")
      some_clean_up()
      raise

or probably better

try:
     operation()
except Exception as err:
     if isinstance(err, IOError) and err.errno == 2:
        do_something()
     else:
         logger.error("Error performing operation: {}".format(err.message)")
         some_clean_up()
         raise

-- 
Terry Jan Reedy