python / python/mypy

assignment to `_` inside a function incorrectly becomes `Any`

Open
#17,697 2 comments 1 reaction 0 assignees View on GitHub

Nobody has claimed this yet.

bug
Dominant language
Python
Stars
20.6k
Forks
3.3k
PR merge metrics
PR metrics pending

Description

def foo() -> None:
    _ = [1] # error: no-any-expr

playground

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by reproducing the example in the linked mypy playground with the shown strictness flags, then trace how assignment to _ is inferred inside a function. Done means the example no longer incorrectly reports no-any-expr because the assignment has become Any.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
compilers
Issue type
Bug
Difficulty
3/5
Estimated time
1-2 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

Get new issues in your inbox

A short digest of beginner-friendly GitHub issues.