[code-quality] Alerting to unused module globals, instance attributes, etc?

[Skip Montanaro]

On Wed, Apr 23, 2014 at 9:28 AM, Phil Frost <indigo at bitglue.com>
wrote:
> Rather than make guesses that are right 90% of the time and yield 10%
> false positives, pyflakes takes the PEP 20 approach:
...
> It is the opinion of pyflakes that determining the correctness of your
> program in such complex situations is better served by unit tests.

Thanks for the response. How would a unit test tell me a particular
method or data attribute is unused within the module? And if the
attribute used to be used, but no longer is (and should be deleted to
ease maintenance), does a unit test keep it alive?

The main Python code base I work with is now more than 10 years old,
and was not designed at the outset to easily support the creation of
unit tests.  (Numbers-wise, it's nearly 50kloc in over 200 Python
files.)  It also grew organically as requirements and focus of the
code changed. I'm sure there's now a ton of unused code in there I
could just discard.  Finding it can be a challenge.  Just because an
attribute isn't used within a module doesn't mean it's dead, but in
certain situations it would be nice if a checker could at least warn
me, "hey, I see that you assigned to 'self.foo', but I don't see any
obvious uses of that attribute within the class or module."  I would
be more than happy with a 90% hit rate on such stuff.  I don't care
about perfection here.  I don't care about the craziness of assigning
something bizarre to "self" or use of getattr and its cousins.  I also
would be happy if I needed to set a config variable or add a command
line flag to enable such behavior.

And if we are using the Zen of Python as our guide:

    Special cases aren't special enough to break the rules.
    Although practicality beats purity.

I'm looking for practicality here, not purity.

Skip