Registry / serialization / marshmallow-fastoneofschema

marshmallow-fastoneofschema

library2025.9.2.1.dev7pypypi✓ verified 85d ago

A fast multiplexing schema for marshmallow that dispatches deserialization to a subschema based on a discriminator field. Uses schema caching for speed. Current version (2025.9.2.1.dev7) is a development release; requires Python >=3.11.

serialization

pip install marshmallow-fastoneofschema

github ↗package ↗

INSTALL

IMPORT

SIG · MARSHMALLOW-FASTON

marshmallow-fastoneofschema

serializationpythonv2025.9.2.1.dev7

Install

1.6s avg

Import

—

Disk

15MB

Pass rate

6/ 10

Env Coverage6 / 10

glibc

3.9–3.13

musl

3.9–3.13

Install & Compatibility

Where this runs

tested against v2025.9.2.1.dev7 · pip install

no network on importno background threads

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

glibc

py 3.10

✕ build_error

py 3.11

✓ —

✓ 1.7s

py 3.12

✓ —

✓ 1.5s

py 3.13

✓ —

✓ 1.5s

py 3.9

✕ build_error

15MB installed

● package 15MB

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

FastOneOfSchema

✓ from marshmallow_fastoneofschema import FastOneOfSchema

Demonstrates basic usage: define a FastOneOfSchema with a discriminator field and subschemas.

from marshmallow import Schema, fields from marshmallow_fastoneofschema import FastOneOfSchema class CarSchema(Schema): make = fields.String(required=True) model = fields.String(required=True) class BoatSchema(Schema): length = fields.Float(required=True) class VehicleSchema(FastOneOfSchema): type_field = 'vehicle_type' type_schemas = { 'car': CarSchema, 'boat': BoatSchema } schema = VehicleSchema() data = {'vehicle_type': 'car', 'make': 'Toyota', 'model': 'Camry'} result = schema.load(data) print(result) # => {'vehicle_type': 'car', 'make': 'Toyota', 'model': 'Camry'}

Debug

Known issues

gotchaThe `type_field` must be present in the input data and must match one of the keys in `type_schemas`. Missing or mismatched values cause a validation error.

fix

Ensure each input dict contains the discriminator field with a valid value.

affects: all

gotchaFastOneOfSchema caches the mapping from type_field value to schema. If you mutate `type_schemas` after instantiation, the cache may become stale.

fix

Define `type_schemas` as a class variable or set it before any call to load/dump.

affects: all

deprecatedPreviously, the discriminator field was set via `type_field` as a class variable. Some older examples used `type_field_` (with underscore). The correct attribute is `type_field`.

fix

Use `type_field` (without trailing underscore) as the class variable or constructor argument.

affects: <2025.9.2.1

Errors

Common errors & fixes

ImportError: cannot import name 'FastOneOfSchema' from 'marshmallow_fastoneofschema'

Old version or incorrect library installed (e.g., same name but different package).

fix

Run `pip install --upgrade marshmallow-fastoneofschema` and ensure you have a recent version (>=2025.9.2.1.dev0).

marshmallow.exceptions.ValidationError: {'_schema': ['Invalid type field value']}

The discriminator field value does not match any key in `type_schemas`.

fix

Check that the input contains a valid discriminator value, e.g., one of the keys defined in `type_schemas`.

Upgrade

Version history

2025.9.2.1.dev7latest on PyPI · released Sep 2, 2025

Audit

Dependencies

marshmallowrequiredCore framework dependency

Agent activity

6 hits · last 30 days

node

Resources

githubhttps://github.com/Kalepa/marshmallow-fastoneofschema ↗

packagehttps://pypi.org/project/marshmallow-fastoneofschema/ ↗