It is currently a general convention in asyncio to only catch Exception, not BaseException. I consider this a flaw and we should fix it, but it's unfortunately not so easy -- the tests will fail if you replace all occurrences of Exception with BaseException, and it is not always clear what's the right thing to do. E.g. catching KeyboardInterrupt may actually make it harder to stop a runaway asyncio app.

We should move this discussion to the issue tracker.

On Mon, Jun 4, 2018 at 9:11 AM, Victor Stinner <vstinner@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.

Victor
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