python / python/mypy

Support enum square bracket notation

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#6,135 1 comment 0 reactions 0 assignees View on GitHub

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feature priority-2-low topic-enum
Dominant language
Python
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Description

Enums can not always be accessed with .-notation, like in the example below.

import enum
import operator

OperatorEnum = enum.Enum(
    "OperatorEnum",
    {"==": operator.eq, ">=": operator.ge, "<=": operator.le, ">": operator.gt, "<": operator.lt},
)

OperatorEnum["foo"]  # pass, but should throw an error?
OperatorEnum.foo  # Fails

It would be great if OperatorEnum["foo"] is caught by mypy.

Contributor guide

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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 reported enum example with mypy and inspect the checker entry point for enum member access and subscription expressions. Done means mypy reports an error for OperatorEnum["foo"] while preserving valid enum access behavior.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
devtools
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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