python-attrs/cattrs

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Composable custom class converters for attrs, dataclasses and friends.

Stars: 1.1k
Forks: 159
Open beginner issues: 0
Indexed issues: 80
Avg merge: 12h 21m
Merged PRs (30d): 6

Dominant language: Python
License: MIT
Last GitHub push: Sep 14, 2026
Latest indexed: Sep 20, 2026
Contributing guide: Contributing guide
Code of conduct: Code of conduct
Beginner labels: No beginner labels indexed

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80 issues indexed so far

Literal discriminator ignores override(rename=...), so union structuring fails with KeyError Open

Difficulty 2/5 1-3 hours Newbie friendliness 35/100

python-attrs/cattrs#779 · Opened Sep 17, 2026
msgpack and cbor2 serialize naive datetimes using the encoding machine's local timezone Open

Difficulty 3/5 1-2 days Newbie friendliness 85/100

python-attrs/cattrs#774 · Opened Sep 1, 2026
decimal.Decimal not handled in preconf converters (json, pyyaml) Open

Difficulty 2/5 1-3 hours Newbie friendliness 72/100

python-attrs/cattrs#761 · 2 comments · Opened Jun 26, 2026
Structure/unstructure decorators for classes Open

Difficulty 5/5 Over a week Newbie friendliness 35/100

python-attrs/cattrs#746 · 2 comments · Opened Apr 13, 2026
Implement a strategy to resolve natively Sequence[X] | Y Open

Difficulty 4/5 3-5 days Newbie friendliness 45/100

python-attrs/cattrs#743 · 2 comments · Opened Apr 1, 2026
omit_if_default ignores attrs' converters Open

Difficulty 3/5 1-2 days Newbie friendliness 35/100

python-attrs/cattrs#695 · 2 comments · Opened Oct 28, 2025
Validation errors from multiple fields are not in ClassValidationError Open

validation

Difficulty 4/5 3-5 days Newbie friendliness 45/100

python-attrs/cattrs#694 · 7 comments · Opened Oct 23, 2025
Type Error with tagged Unions (working code but mypy/pyright error) Open

typeform

Difficulty 2/5 1-3 hours Newbie friendliness 52/100

python-attrs/cattrs#690 · 3 comments · Opened Oct 15, 2025
An enum used as another enum's value is not unstructured by the json converter Open

Difficulty 3/5 1-2 days Newbie friendliness 45/100

python-attrs/cattrs#679 · Opened Aug 25, 2025
Using several factories simultaneously Open

Difficulty 5/5 Over a week Newbie friendliness 35/100

python-attrs/cattrs#659 · 7 comments · Opened Jun 18, 2025
Support tagged unions when the discriminator field is in a generic wrapper, not in the union type Open

Difficulty 4/5 3-5 days Newbie friendliness 48/100

python-attrs/cattrs#651 · 1 comment · Opened May 26, 2025
Natively support more types with pre-defined optional hooks Open

enhancement

Difficulty 5/5 Over a week Newbie friendliness 30/100

python-attrs/cattrs#641 · 3 comments · Opened Mar 29, 2025
'_UnionGenericAlias' is deprecated and slated for removal in Python 3.17 Open

Difficulty 2/5 1-3 hours Newbie friendliness 45/100

python-attrs/cattrs#635 · 1 comment · 4 reactions · Opened Mar 18, 2025
Enum misuse causes unhelpful error Open

Difficulty 3/5 1-2 days Newbie friendliness 35/100

python-attrs/cattrs#601 · 1 comment · Opened Nov 20, 2024
pyright says that type of cattrs.preconf.json.make_converter is partially unknown Open

Difficulty 2/5 1-3 hours Newbie friendliness 45/100

python-attrs/cattrs#593 · 3 comments · Opened Oct 22, 2024
Union with subclasses Open

Difficulty 4/5 3-5 days Newbie friendliness 38/100

python-attrs/cattrs#583 · 1 comment · Opened Sep 27, 2024
Extra keys Open

Difficulty 5/5 Over a week Newbie friendliness 35/100

python-attrs/cattrs#580 · 2 comments · Opened Sep 13, 2024
[Feature] Use typing.Annotated for customization Open

Difficulty 5/5 Over a week Newbie friendliness 35/100

python-attrs/cattrs#571 · 12 comments · 1 reaction · Opened Aug 19, 2024
`make_unstructure_dict_unstructure_fn` does not honor `use_class_methods` Open

Difficulty 5/5 Over a week Newbie friendliness 35/100

python-attrs/cattrs#566 · Opened Aug 1, 2024
Preconfigured union for a "plain" python data structures Open

Difficulty 3/5 1-2 days Newbie friendliness 45/100

python-attrs/cattrs#554 · Opened Jul 13, 2024
base64 pre-config option Open

Difficulty 3/5 1-2 days Newbie friendliness 45/100

python-attrs/cattrs#552 · 1 comment · Opened Jul 10, 2024
Derived class disambiguating fails, but only sometimes. Open

more-info-needed

Difficulty 4/5 3-5 days Newbie friendliness 35/100

python-attrs/cattrs#544 · 4 comments · Opened Jun 5, 2024
Inheriting overrides Open

Difficulty 5/5 Over a week Newbie friendliness 35/100

python-attrs/cattrs#538 · 3 comments · Opened May 19, 2024
Subclass disambiguation for nested structures. Open

more-info-needed question

Difficulty 4/5 3-5 days Newbie friendliness 35/100

python-attrs/cattrs#535 · 3 comments · Opened Apr 23, 2024
TYPE_CHECKING and init=False Open

enhancement

Difficulty 3/5 1-2 days Newbie friendliness 45/100

python-attrs/cattrs#531 · 7 comments · 1 reaction · Opened Apr 15, 2024
How to hook into structuring of a simple dict? Open

more-info-needed

Difficulty 4/5 3-5 days Newbie friendliness 25/100

python-attrs/cattrs#524 · 6 comments · Opened Mar 18, 2024
[macOS] Error when trying to run tests: `ImportError: cannot import name 'CodecOptions' from 'bson'` Open

more-info-needed

Difficulty 3/5 1-2 days Newbie friendliness 28/100

python-attrs/cattrs#523 · 2 comments · Opened Mar 18, 2024
Dataclass structuring fails with misleading error message. Open

Difficulty 3/5 1-2 days Newbie friendliness 48/100

python-attrs/cattrs#521 · 2 reactions · Opened Mar 14, 2024
How to recursively unstructure with hooks? Open

Difficulty 4/5 3-5 days Newbie friendliness 28/100

python-attrs/cattrs#520 · 5 comments · Opened Mar 14, 2024
Documentation does not explain unstruct_collection_overrides' input Open

Difficulty 2/5 1-3 hours Newbie friendliness 64/100

python-attrs/cattrs#513 · 4 comments · Opened Feb 27, 2024
KeyError when using configure_tagged_union with existing field Open

more-info-needed

Difficulty 2/5 1-3 hours Newbie friendliness 50/100

python-attrs/cattrs#483 · 3 comments · Opened Jan 13, 2024
Option to include `init=False` globally on a converter, not per class Open

documentation

Difficulty 4/5 3-5 days Newbie friendliness 35/100

python-attrs/cattrs#482 · 2 comments · Opened Jan 10, 2024
Using class methods strategy for structuring Enums fails without clear info Open

enhancement

Difficulty 4/5 3-5 days Newbie friendliness 42/100

python-attrs/cattrs#479 · 4 comments · Opened Jan 3, 2024
When structuring, how to forbid type casting to base classes? Open

enhancement

Difficulty 4/5 3-5 days Newbie friendliness 25/100

python-attrs/cattrs#469 · 2 comments · Opened Dec 12, 2023
`cattrs.structure` is failing `detailed_validation=True` behavior with validations Open

enhancement

Difficulty 3/5 1-2 days Newbie friendliness 45/100

python-attrs/cattrs#440 · 6 comments · Opened Nov 3, 2023
Dynamic strategy for subclasses Open

Difficulty 5/5 Over a week Newbie friendliness 25/100

python-attrs/cattrs#434 · 2 comments · Opened Oct 19, 2023
Type validation on unstructure Open

enhancement

Difficulty 5/5 Over a week Newbie friendliness 25/100

python-attrs/cattrs#433 · 1 comment · Opened Oct 18, 2023
attrs 23.1.0 breaks string annotated generics Open

blocked-upstream bug

Difficulty 3/5 1-2 days Newbie friendliness 45/100

python-attrs/cattrs#427 · 2 comments · 1 reaction · Opened Sep 19, 2023
Better Union resolution Open

enhancement

Difficulty 4/5 3-5 days Newbie friendliness 35/100

python-attrs/cattrs#423 · 3 comments · 3 reactions · Opened Aug 30, 2023
cattrs does not unstructure os.PathLike to str Open

Difficulty 3/5 1-2 days Newbie friendliness 42/100

python-attrs/cattrs#417 · 3 comments · Opened Aug 17, 2023
Check if the data can be structured without actually structuring it Open

enhancement

Difficulty 5/5 Over a week Newbie friendliness 25/100

python-attrs/cattrs#414 · 7 comments · Opened Aug 10, 2023
How to deserialize multidict to data model? Open

question

Difficulty 4/5 3-5 days Newbie friendliness 35/100

python-attrs/cattrs#407 · 6 comments · Opened Aug 4, 2023
Pass type information to `format_exception` from `transform_errors` for primitive types Open

Difficulty 3/5 1-2 days Newbie friendliness 35/100

python-attrs/cattrs#401 · Opened Jul 29, 2023
Schema generation Open

Difficulty 5/5 Over a week Newbie friendliness 25/100

python-attrs/cattrs#397 · 10 comments · 6 reactions · Opened Jul 24, 2023
Unstructuring subclasses Open

Difficulty 4/5 3-5 days Newbie friendliness 35/100

python-attrs/cattrs#354 · 2 comments · Opened Apr 14, 2023
Feature request: "flatten" operation for cattrs.gen Open

Difficulty 4/5 3-5 days Newbie friendliness 45/100

python-attrs/cattrs#352 · 3 reactions · Opened Apr 12, 2023
Support subset of tagged union strategy Open

Difficulty 4/5 3-5 days Newbie friendliness 45/100

python-attrs/cattrs#348 · Opened Apr 6, 2023
Can't use disambiguation strategy together with `Optional` Open

Difficulty 3/5 1-2 days Newbie friendliness 42/100

python-attrs/cattrs#345 · 4 comments · Opened Mar 29, 2023
Custom unstructure function is not called when a union type is wrapped in generic types multiple times Open

Difficulty 3/5 1-2 days Newbie friendliness 45/100

python-attrs/cattrs#336 · 3 comments · Opened Mar 6, 2023
Lambda passed to register_unstructure_hook is not called for an instance when instance is in an inherited field Open

Difficulty 3/5 1-2 days Newbie friendliness 45/100

python-attrs/cattrs#335 · 1 comment · Opened Mar 5, 2023

python-attrs/cattrs

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