[openstack-dev] [nova] 'if foo' vs 'if foo is not None'

Andrew Laski andrew.laski at rackspace.com
Mon Mar 3 15:41:32 UTC 2014

On 03/03/14 at 03:00pm, Matthew Booth wrote:
>PEP 8, under 'Programming Recommendations' recommends against implicit
>comparison to None. This isn't just stylistic, either: we were actually
>bitten by it in the VMware driver
>(https://bugs.launchpad.net/nova/+bug/1262288). The bug was hard to
>spot, and had consequences to resource usage.
>However, implicit comparison to None seems to be the default in Nova. Do
>I give up mentioning this in reviews, or is this something we care about?

 From what I've seen I don't think it's implicit comparison to None so 
much as it's considering None and things like [] to be equal.  Because 
there is a risk of bugs, and I've seen others beyond the one linked 
above, I think it's worth pointing out in a review.  But the context has 
to be taken into account as sometimes it's legitimate to consider None 
and [] to be equal.

>Matthew Booth, RHCA, RHCSS
>Red Hat Engineering, Virtualisation Team
>GPG ID:  D33C3490
>GPG FPR: 3733 612D 2D05 5458 8A8A 1600 3441 EA19 D33C 3490
>OpenStack-dev mailing list
>OpenStack-dev at lists.openstack.org

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