[openstack-dev] Dropping or weakening the 'only import modules' style guideline - H302

Robert Collins robertc at robertcollins.net
Tue Aug 6 02:26:20 UTC 2013

I wanted to get a temperature reading from everyone on this style guideline.

My view on it is that it's a useful heuristic but shouldn't be a
golden rule applied everywhere. Things like matches are designed to be
used as a dsl:
    self.assertThat(foo, Or(Equals("1"), Equals("2")))

rather than what H302 enforces:
    self.assertThat(foo, matchers.Or(matchers.Equals("1"),

Further, conflicting module names become harder to manage, when one
could import just the thing.

Some arguments for requiring imports of modules:
 - makes the source of symbols obvious
   - Actually, it has no impact on that as the import is still present
and clear in the file. import * would obfuscate things, but I'm not
arguing for that.
   - and package/module names can (and are!) still ambiguous. Like
'test.' - whats that? -> consult the imports.
 - makes mocking more reliable
   - This is arguably the case, but it's a mirage: it isn't a complete
solution because modules still need to be mocked at every place they
are dereferenced : only import modules helps to the extent that one
never mocks modules. Either way this failure mode of mocking is
usually very obvious IME : but keeping the rule as a recommendation,
*particularly* when crossing layers to static resources is a good
 - It's in the Google Python style guide
   - shrug :)

What I'd like us to do is weaken it from a MUST to a MAY, unless noone
cares about it at all, in which case lets just turn it off entirely.


Robert Collins <rbtcollins at hp.com>
Distinguished Technologist
HP Converged Cloud

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