Suggestion: When eq=Callable, make __hash__ use the return value of the callable.
Nobody has claimed this yet.
Assessment
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Newbie friendliness
- 42/100
- Issue type
- Feature
- Clarity
- Mostly clear
- Activity status
- Stale
- Tech stack
- python
- Domain
- developer-experience
Research direction
Start by tracing how attrs.field(eq=...) is interpreted for an @attrs.frozen class and how the generated hash handles that field. Compare the proposed hash=True and hash=key_func APIs, then add focused coverage showing that equality and hashing remain consistent; done means the example can be used as a dictionary key without a custom hash.
Written by the indexing model from the issue text.
Description
The specific situation is more complicated, but this is the minimal representation. I have a situation where I have a datastructure that is "frozen" and my contract with myself is I promise not to edit any of the values in it. But I can't use the attrs datastructure as a dict key because a field is mutable and unhashable.
def key_func(field: dict[str, str]):
return sorted(field.keys())
@attrs.frozen
class Example:
other: int
field: dict[str, str]: attrs.field(eq=key_func)
I've "solved" this by adding the hash method:
def __hash__(self):
return hash((self.other, key_func(self.field)))
But it would be nice if we could do this natively via the API.
If necessary, either of these incantations seem sensible: attrs.field(eq=key_func, hash=True) or attrs.field(eq=key_func, hash=key_func)
- Dominant language
- Python
- Stars
- 5.8k
- Forks
- 480
- Avg merge
- 2h 15m
- Merged PRs (30d)
- 2
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
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