[Python-Dev] exception chaining (original) (raw)

Terry Reedy tjreedy at udel.edu
Sat Jan 21 07:07:00 CET 2012

On 1/20/2012 7:40 PM, Steven D'Aprano wrote:

Benjamin Peterson wrote:

2012/1/20 Terry Reedy <tjreedy at udel.edu>:

Since 'raise' means 're-raise the current error', 'raise as OtherError' means (clearly to me, anyway) 're-raise the current error as OtherError'.

That doesn't make any sense. You're changing the exception completely not reraising it. I expect Terry is referring to the coder's intention, not the actual nuts and bolts of how it is implemented.

Yes, same error situation, translated, typically from developer language to app language.

def spam(): try: something() except HamError: raise SpamError

is implemented by catching a HamError and raising a completely different SpamError, but the intention is to "replace the HamError which actually occurred with a more appropriate SpamError". At least that is my intention when I write code like the above, and it appears to be the usual intention in code I've seen that uses that idiom. Typically SpamError is part of the function's API while HamError is not.

-- Terry Jan Reedy

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