Hi Stephen,
I think this is a legitimate complaint from pylint. Consider the case where
`job.devices` is an empty iterable (a list with no members, perhaps). In
that case, neither the name `device_id` nor the name `device` will have
been bound to any object, and therefore, there's no way to satisfy the
`del` statement.
Indeed, if you run a simple program like this:
collect = []
# collect = ["hello"] # for comparison
for member in collect:
value = member.upper()
del member
del value
You get the same pylint warning, but better yet, you get a `NameError`
raised at the point of the `del`. Your suggestion of moving the loop to the
function would alleviate the problem, since there would be no need for the
explicit `del`. If that's unavoidable, you could add an explicit `device =
device_id = None` before the start of the for loop.
Hope this helps!
tjs
On Fri, Sep 20, 2019 at 5:17 PM Stephen Satchell <l...@satchell.net> wrote:
> This is a minor thing, but it is puzzling. Here is a code fragment from
> a project I'm working on:
>
> > for device_id in job.devices:
> > device = job.devices[device_id]
> > <loop>
> > del device_id
> > del device
>
> When I run pylint (version 1.6.5, astroid 1.4.9) against this code, I
> get one warning diagnostic:
>
> > Using possibly undefined loop variable 'device_id'
> (undefined-loop-variable)
>
> Experimenting with Python 2, the loop variable is indeed in the name
> space of the function I'm running. I get the same result with Python 3,
> the loop variable is indeed in the function namespace.
>
> The reason I'm using 'del' is to avoid name collisions on other sections
> of code being written at different times -- this project has gone two
> months already.
>
> My "workaround" is to remove the del statement for the loop variable,
> and leaving the rest of the del statements in for variables inside the
> loop that (being a ex PL/1 programmer) I would assume would be out of
> scope, but aren't.
>
> I may move this loop into a separate function, and remove the need for
> the del statements.
>
> Comments?
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--
Tim Stumbaugh
Trading Control
Hudson River Trading
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