
2009/7/18 Steven D'Aprano <steve@pearwood.info>
On Sat, 18 Jul 2009 09:41:10 am Michael wrote:
Here are two examples of why allowing return inside a finally block is a bad idea:
def f(): try: return 3 finally: return 4
Given that the finally block is guaranteed to run after exiting the try block, I don't see anything objectionable about that. Surprising, perhaps, possibly even an artifact of the CPython implementation, but why is it a "bad idea" that needs to be protected against?
It's arbitrary - and constructs with arbitrary interpretations are generally not a *good* thing at the very least. It also makes it harder to read code, where a return in a try:... finally block may not do anything.
def f(): try: raise Exception() finally: return 4
That's no weirder than:
def f(): try: raise Exception() except Exception: return 4
or:
def f(): try: raise Exception() except Exception: pass return 4
It is much weirder. In the case of explicitly using an except you are catching the error and choosing not to propagate it. In a finally where the normal semantics are that the exception is re-raised the return silently circumvents that. Michael
-- Steven D'Aprano _______________________________________________ Python-ideas mailing list Python-ideas@python.org http://mail.python.org/mailman/listinfo/python-ideas