[strongSwan-dev] Python vici library

Martin Willi martin at strongswan.org
Mon Mar 9 12:42:38 CET 2015

Hi Björn,

Thanks for reviewing these changes.

> Nice start on the README. I took a moment to make the python part a bit
> more "pythonic", and pushed it to a branch on github:

Thanks for the fixes, I've squashed them into the associated commits in
my branch.

> I've taken a look at your code changes. I definitely agree that
> implicit error checking is nicer, and it will make the experience of
> using the library much smoother. There is a problem with your
> implementation however, you are discarding any errors for commands that
> require event streaming 

Correct, I've tried to address this with [1].

> While generators is a good idea for response streaming, it is not a great
> fit here. The current implementation works on the assumption that the
> generator is exhausted before another command starts. There is no way to
> guarantee this, as the user may draw elements from the generator as he/she
> wishes.

While I agree at some point, IMHO this is how generators in Python work.
The user should call call close() on it, either implicitly by breaking
from the iteration loop, or explicitly when manually iterating using

Ideally, if the user does so we would unsubscribe from the events, and
prematurely return from the associated command. However, this is
currently not supported in vici at the daemon side, but we might extend
that in the future.
Instead, I'm just stopping calling yield once a GeneratorExit exception
gets raised. This makes sure the protocol stays in sync, but stops
returning results to the caller. This is implemented with [2].

> >>> g = s.list_certs()
> >>> msg = next(g)
> >>> print s.version()

While this example still fails, the following should work as expected:

>>> g = s.list_certs()
>>> msg = next(g)
>>> g.close()
>>> print s.version()

I think with these changes, the advantages we get with the generator
approach at least compensate for the disadvantages, given that most
users iterate using "for" loops.

Best regards


More information about the Dev mailing list