[Python-Dev] Why not using "except: (...) raise" to cleanup on error?

Chris Angelico rosuav at gmail.com
Mon Jun 4 12:42:09 EDT 2018

On Tue, Jun 5, 2018 at 2:11 AM, Victor Stinner <vstinner at redhat.com> wrote:
> Hi,
> I just read a recent bugfix in asyncio:
> https://github.com/python/cpython/commit/9602643120a509858d0bee4215d7f150e6125468
> + try:
> +     await waiter
> + except Exception:
> +     transport.close()
> +     raise
> Why only catching "except Exception:"? Why not also catching
> KeyboardInterrupt or MemoryError? Is it a special rule for asyncio, or
> a general policy in Python stdlib?
> For me, it's fine to catch any exception using "except:" if the block
> contains "raise", typical pattern to cleanup a resource in case of
> error. Otherwise, there is a risk of leaking open file or not flushing
> data on disk, for example.

Pardon the dumb question, but why is try/finally unsuitable?


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