[Python-Dev] PEP for allowing 'raise NewException from None'

Ethan Furman ethan at stoneleaf.us
Sat Jan 28 01:33:21 CET 2012

Terry Reedy wrote:
> The PEP does not address the issue of whether the new variation of raise 
> is valid outside of an except block. My memory is that it was not to be 
> and I think it should not be. One advantage of the 'as' form is that it 
> is clear that raising the default as something else is invalid if there 
> is no default.

Were you speaking of the original (PEP 3134), or this new one (PEP 409)?

Because at this point it is possible to do:

     raise ValueError from NameError

outside a try block.  I don't see it as incredibly useful, but I don't 
know that it's worth making it illegal.

So the question is:

   - should 'raise ... from ...' be legal outside a try block?

   - should 'raise ... from None' be legal outside a try block?


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