Remove unused imports - March 2025 Edition

[vstinner]

Feature or enhancement

Proposal:

There are a bunch of unused imports in Python stdlib. I'm working on pull requests to remove them.

Has this already been discussed elsewhere?

No response given

Links to previous discussion of this feature:

No response

Linked PRs

• gh-131152, pkgutil: Remove unused imports #131149
• gh-131152: Remove unused imports from tests #131153
• gh-131152: Remove unused imports from tests (part 2) #131154
• gh-131152: Remove unused imports from Tools/{build,wasm} #131155
• gh-131152: Remove unused imports from Tools/cases_generator #131156
• gh-131152: Remove unused imports in tests #131169

[vstinner]

See also PR gh-131150.

[corona10]

Do you plan to add CI for checking unused imports? cc @hugovk

[vstinner]

Do you plan to add CI for checking unused imports? cc @hugovk

I tried ruff check but it failed to detect many unused imports.

So I used pyflakes as usual, but this tool doesn't take # noqa comments in account. I had to filter the output manually to ignore imports known to be used (ex: import side effects) even if they seem to be unused.

Maybe a ruff check can be used, even if it's incomplete.

[StanFromIreland]

ruff's 401 works great for me. I can open a PR with a few :-)

edit: I went through all of ruffs suggestions

[donBarbos]

today i accidentally came across next unused import :-)

cpython/Lib/code.py

Lines 378 to 381 in f7ac656

	try:
	import readline # noqa: F401
	except ImportError:
	pass

and i'm going to check cli modules from cmdline.rst list (i'll try not to repeat with changes)

[donBarbos]

This command working for me is fine: uvx ruff check ./Lib/ --select F401 --isolated --ignore-noqa
This command found 209 cases only in ./Lib/test/ dir for F401 rule

[donBarbos]

cc @vstinner I can send a PR for each module separately if you are against it.
You have already wrote in description that you are already working on it, that is why I am asking :-)

[vstinner]

import readline # noqa: F401: this import is used. When you import readline, there is a side effect of executing code which makes the command line more usable. That's why there is the # noqa comment: to tell the linter that the import is actually used.

[donBarbos]

import readline # noqa: F401: this import is used. When you import readline, there is a side effect of executing code which makes the command line more usable. That's why there is the # noqa comment: to tell the linter that the import is actually used.

sorry, I'll remember it (but I guessed there was some side effect)

[vstinner]

I close this issue, since the initial issue (unused imports) has been fixed. If someone wants to automate detecting unused imports, I suggest to open a new issue. But be aware that there are reasons why it's not automated yet.

This command found 209 cases only in ./Lib/test/ dir for F401 rule

Be careful, linters are stupid and reports false alarms. I checked ruff check ./Lib/ --select F401 --isolated output: it reports 160 "errors", but I found a single real error (an unused import, I will leave it for now, it's not a big deal). That's why it's not automated yet, the tooling isn't smart enough to ignore unused imports which are actually used.

I added # noqa in some places, but in some others, some developers were against it so I gave up. See:

• gh-120417: Add #noqa to used imports in the stdlib #120421 (merged)
• gh-120417: Add #noqa: F401 to tests #120627 (merged)
• gh-120417: Add more #noqa to used imports in the stdlib #120454 (rejected)
• gh-120417: Add #noqa to load_tests() in tests #120626 (rejected)
• Remove unused imports from the stdlib #120417 (discussion)