Should black remove unused imports?

[MichalPodeszwa]

I've noticed that right now Black doesn't do that.
I'm wondering whether it's something that Black should take care of?

[eplaut]

+1

[Lukas0907]

There is already a tool that does that, btw.: https://github.com/myint/autoflake

[ambv]

I'm afraid this is scope creep and something that can silently break otherwise valid programs. My intuition is to avoid this in Black.

[wyuenho]

Javascript has the same issue and Prettier doesn't seem to have the same qualm in removing unused imports and vars by default. Is there anything special in Python that you can't do with ES modules?

[ichard26]

Imports has some weird side effects sometimes that would probably be really hard to detect statically. See the example here
#333 (comment). The example is a valid set of instructions per se, but it depends on an side effect of importing. Even if pkg.mod2 doesn't seemed to be used, it is needed so the REPL can access pkg.mod which is imported via pkg.mod2.

[wyuenho]

I see. I guess __all__ = [foo, bar] will also make it hard too, since now you have to chase an entire graph to dereference the values too.

[hadialqattan]

Imports has some weird side effects sometimes that would probably be really hard to detect statically. See the example here
#333 (comment). The example is a valid set of instructions per se, but it depends on an side effect of importing. Even if pkg.mod2 doesn't seemed to be used, it is needed so the REPL can access pkg.mod which is imported via pkg.mod2.

I agree with you!

BTW, I've developed a tool to do this task safely, If you are interested please check it out!

Docs: https://hadialqattan.github.io/pycln
Repo: https://github.com/hadialqattan/pycln

[Danipulok]

@ambv is there any example the program could silently break because of unused imports?
Even PyCharm highlights unused imports. And when you need them, can use # noqa (as I and many developers do).
Is there any way you could implement the same logic?

Or at least do it with a specified flag that's disabled by default. In my opinion, it would be really useful.

[ichard26]

An example off the top of my head: readline is a stdlib module commonly used as simply an import. By importing it, history is enabled for input() prompts.

[...] it would be really useful.

Yes it would be useful, but I don't believe this is in scope for Black. Black's focus is code style, not code optimization or linting. Other tools can and should handle those; I don't want to be in the business of writing an autofixer for linting issues.