marshmallow-code/marshmallow

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A lightweight library for converting complex objects to and from simple Python datatypes.

Stars: 7.2k
Forks: 738
Open beginner issues: 0
Indexed issues: 117
Avg merge: 1d 23h
Merged PRs (30d): 7

Dominant language: Python
License: MIT
Last GitHub push: Sep 15, 2026
Latest indexed: Sep 19, 2026
Contributing guide: Contributing guide
Code of conduct: Code of conduct
Beginner labels: help wanted

Beginner friendly Everything

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117 open issues indexed

[Bug] Negative POSIX timestamps cannot be deserialized after timestamp serialization Open

Difficulty 2/5 1-3 hours Newbie friendliness 84/100

marshmallow-code/marshmallow#3019 · 2 comments · Opened Aug 13, 2026
Inconsistent value type when validating nested schema fields Open

Difficulty 3/5 1-2 days Newbie friendliness 55/100

marshmallow-code/marshmallow#2961 · 4 comments · Opened Apr 27, 2026
Dependency Dashboard Open

Difficulty 2/5 1-3 hours Newbie friendliness 25/100

marshmallow-code/marshmallow#2953 · Opened Apr 13, 2026
Feature - allow inheriting load_default from nested schema populated with from_dict Open

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

marshmallow-code/marshmallow#2889 · 2 comments · Opened Jan 6, 2026
Consistency with allow_none with serialization and deserialization Open

Difficulty 3/5 1-2 days Newbie friendliness 55/100

marshmallow-code/marshmallow#2836 · 1 comment · 1 reaction · Opened Jul 16, 2025
SchemaOpts misses partial Open

Difficulty 2/5 1-3 hours Newbie friendliness 68/100

marshmallow-code/marshmallow#2834 · Opened Jun 24, 2025
'NoneType' object is not subscriptable when serializing fields that do not belong to the database is None Open

question

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

marshmallow-code/marshmallow#2833 · 3 comments · Opened Jun 20, 2025
Removing Schema context feels like a bad idea! Open

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

marshmallow-code/marshmallow#2832 · 3 comments · Opened Jun 20, 2025
Is there a way to pre-define built-in validators that can be used multiple times? Open

question

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

marshmallow-code/marshmallow#2829 · 2 comments · Opened Jun 3, 2025
Extra documentation for new context implementation? Open

polymorphism question

Difficulty 3/5 1-2 days Newbie friendliness 30/100

marshmallow-code/marshmallow#2824 · 21 comments · Opened Apr 24, 2025
TimeDelta misleading 'precision' argument & v4 breaking change Open

feedback welcome

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

marshmallow-code/marshmallow#2822 · 3 comments · Opened Apr 21, 2025
Dump converts int or bool to float Open

polymorphism

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

marshmallow-code/marshmallow#2816 · 1 comment · Opened Mar 31, 2025
Remove `only`, `exclude`, `many`, and `unknown` parameters of `Nested` and require callables to return Schema instances Open

backwards incompat feedback welcome

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

marshmallow-code/marshmallow#2794 · 1 comment · Opened Jan 19, 2025
fields.URL validation error should specify "not a valid FQDN" if trying to pass hostname without domain Open

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

marshmallow-code/marshmallow#2243 · 2 comments · Opened Feb 20, 2024
Dot in key is not parsed correclty on loads() Open

docs

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

marshmallow-code/marshmallow#2194 · 3 comments · Opened Oct 5, 2023
[RFC] Add BigInt, SmallInt,... fields. Open

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

marshmallow-code/marshmallow#2182 · 3 comments · Opened Sep 11, 2023
Are nested options applied correctly? Open

Difficulty 3/5 1-2 days Newbie friendliness 38/100

marshmallow-code/marshmallow#2180 · 1 comment · Opened Sep 1, 2023
Doubly Nested Schemas instantiated via lambdas cannot be referenced with multiple dot notation with onlys/excludes Open

Difficulty 3/5 1-2 days Newbie friendliness 38/100

marshmallow-code/marshmallow#2165 · 3 comments · 2 reactions · Opened Aug 11, 2023
Allow 'load_default' for required fields since they can be used with partial. Open

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

marshmallow-code/marshmallow#2151 · 3 comments · Opened Jul 19, 2023
Add ability to set partial default in Meta class Open

Difficulty 3/5 1-2 days Newbie friendliness 38/100

marshmallow-code/marshmallow#2103 · 2 comments · 1 reaction · Opened Feb 17, 2023
Emit warning when user passes string instead of list to OneOf Open

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

marshmallow-code/marshmallow#2074 · 1 comment · Opened Nov 25, 2022
Include a nested relation to one schema, without modifying the rest of the functions that use it Open

Difficulty 5/5 Over a week Newbie friendliness 20/100

marshmallow-code/marshmallow#2069 · 2 comments · Opened Nov 10, 2022
Allow_none in additional parameters Open

question

Difficulty 3/5 1-2 days Newbie friendliness 25/100

marshmallow-code/marshmallow#2043 · 1 comment · Opened Sep 1, 2022
Bug: several nested partial issues (sequence partial, data key, schema initialized partial) Open

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

marshmallow-code/marshmallow#2041 · 8 comments · Opened Aug 31, 2022
[RFC] Don't pass attr, obj, data to fields (de)serialize methods Open

backwards incompat feedback welcome

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

marshmallow-code/marshmallow#2039 · 8 comments · Opened Aug 25, 2022
Format datetime field with millisecond precision Open

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

marshmallow-code/marshmallow#2032 · 1 comment · Opened Aug 9, 2022
Custom Field Logic Bypass Open

docs

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

marshmallow-code/marshmallow#2012 · 4 comments · Opened Jul 18, 2022
Object class and schema definition combined, ORM-style Open

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

marshmallow-code/marshmallow#2000 · 5 comments · 6 reactions · Opened Jun 9, 2022
Can/should marshmallow include pre-built validates_schema methods? Open

polymorphism

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

marshmallow-code/marshmallow#1988 · 3 comments · Opened May 23, 2022
To customize the error message for required fields, pass a dict with a required key as the error_messages argument for the field. Open

Difficulty 3/5 1-2 days Newbie friendliness 25/100

marshmallow-code/marshmallow#1985 · 1 comment · Opened May 5, 2022
Non-obvious error when using fields.Nested with schema instance and many Open

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

marshmallow-code/marshmallow#1982 · 3 reactions · Opened May 3, 2022
be more verbose: marshmallow.exceptions.ValidationError: {'_schema': ['Invalid input type.']} Open

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

marshmallow-code/marshmallow#1975 · 1 comment · 4 reactions · Opened Apr 17, 2022
When deserializing/serializing in a spark job _Missing fileds throw TypeErrrors Open

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

marshmallow-code/marshmallow#1974 · Opened Apr 12, 2022
Should the type of `missing` be exposed publicly for use in type annotations? Open

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

marshmallow-code/marshmallow#1971 · 3 comments · Opened Apr 1, 2022
[RFC] Merge child Schema Meta with inherited parent Meta Open

backwards incompat

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

marshmallow-code/marshmallow#1969 · 2 comments · Opened Mar 29, 2022
load many functionality doesn't seem to be of much help Open

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

marshmallow-code/marshmallow#1964 · Opened Mar 24, 2022
pre_validate decorator Open

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

marshmallow-code/marshmallow#1961 · 2 comments · Opened Mar 20, 2022
Allow conditionally disabling fields Open

polymorphism

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

marshmallow-code/marshmallow#1953 · 1 comment · Opened Mar 2, 2022
Different order of pre_load hooks for List(Nested) and Nested(many=True) fields Open

Difficulty 4/5 3-5 days Newbie friendliness 32/100

marshmallow-code/marshmallow#1942 · 1 comment · Opened Feb 2, 2022
Number fromhex() Open

docs

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

marshmallow-code/marshmallow#1941 · 3 comments · Opened Feb 1, 2022
Convert fields to optional if parent's field has a specific value Open

question

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

marshmallow-code/marshmallow#1940 · Opened Jan 28, 2022
Default error messages not getting overridden Open

question

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

marshmallow-code/marshmallow#1910 · 1 comment · Opened Nov 11, 2021
[validate.oneOf] Returning labels? Open

backwards incompat

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

marshmallow-code/marshmallow#1895 · 1 comment · Opened Oct 27, 2021
Add a "default_dump_fields" or similar parameter to the schema definition Open

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

marshmallow-code/marshmallow#1893 · 1 comment · Opened Oct 24, 2021
Meta Decorator Open

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

marshmallow-code/marshmallow#1879 · 12 comments · 3 reactions · Opened Sep 15, 2021
Always set data_key Open

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

marshmallow-code/marshmallow#1864 · 2 comments · Opened Aug 13, 2021
Schema.dump_only returns empty set if fields explicitly declared dump_only Open

Difficulty 2/5 1-3 hours Newbie friendliness 74/100

marshmallow-code/marshmallow#1857 · 2 comments · 1 reaction · Opened Jul 29, 2021
email validation should support single character TLDs Open

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

marshmallow-code/marshmallow#1844 · Opened Jul 7, 2021
Should marshmallow v5 set required names for hooks? Open

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

marshmallow-code/marshmallow#1841 · Opened Jun 30, 2021
Validating file uploads in Flask Marshmallow Open

question

Difficulty 5/5 Over a week Newbie friendliness 20/100

marshmallow-code/marshmallow#1830 · Opened Jun 15, 2021

marshmallow-code/marshmallow

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