{"library":"marshmallow-oneofschema","title":"Marshmallow OneOfSchema","description":"marshmallow-oneofschema provides polymorphic schema capabilities for Marshmallow, allowing a single schema to serialize and deserialize objects of different types based on a discriminator field. The current version is 3.2.0, and it follows the release cadence of the core Marshmallow library, with stable and well-tested releases.","language":"python","status":"active","last_verified":"Wed May 13","install":{"commands":["pip install marshmallow-oneofschema"],"cli":null},"imports":["from marshmallow_oneofschema import OneOfSchema"],"auth":{"required":false,"env_vars":[]},"quickstart":{"code":"from marshmallow import Schema, fields\nfrom marshmallow_oneofschema import OneOfSchema\n\nclass CatSchema(Schema):\n    name = fields.String(required=True)\n    lives = fields.Integer(load_default=9)\n\nclass DogSchema(Schema):\n    name = fields.String(required=True)\n    breed = fields.String()\n\nclass PetSchema(OneOfSchema):\n    type_schemas = {\n        \"cat\": CatSchema,\n        \"dog\": DogSchema,\n    }\n    type_field = \"pet_type\" # Discriminator field in input data\n\n# Example data\ncat_data = {\"pet_type\": \"cat\", \"name\": \"Whiskers\", \"lives\": 7}\ndog_data = {\"pet_type\": \"dog\", \"name\": \"Buddy\", \"breed\": \"Golden Retriever\"}\nunknown_pet_data = {\"pet_type\": \"fish\", \"name\": \"Nemo\"}\n\n# Instantiate the polymorphic schema\npet_schema = PetSchema()\n\n# Serialization (dump)\nserialized_cat = pet_schema.dump(cat_data)\nprint(f\"Serialized Cat: {serialized_cat}\")\n\nserialized_dog = pet_schema.dump(dog_data)\nprint(f\"Serialized Dog: {serialized_dog}\")\n\n# Deserialization (load)\nloaded_cat = pet_schema.load(serialized_cat)\nprint(f\"Loaded Cat: {loaded_cat}\")\n\nloaded_dog = pet_schema.load(serialized_dog)\nprint(f\"Loaded Dog: {loaded_dog}\")\n\ntry:\n    # This will raise a ValidationError because 'fish' is not in type_schemas\n    pet_schema.load(unknown_pet_data)\nexcept Exception as e:\n    print(f\"Error loading unknown type: {e}\")","lang":"python","description":"This quickstart demonstrates how to define a `OneOfSchema` to handle different types of pet objects (Cat and Dog). It shows how to map type identifiers to specific Marshmallow schemas using `type_schemas` and how to specify the discriminator field using `type_field`. It also includes examples of both serialization (`dump`) and deserialization (`load`), and demonstrates handling an unknown type during deserialization.","tag":null,"tag_description":null,"last_tested":"2026-04-24","results":[{"runtime":"python:3.10-alpine","exit_code":1},{"runtime":"python:3.10-slim","exit_code":1},{"runtime":"python:3.11-alpine","exit_code":1},{"runtime":"python:3.11-slim","exit_code":1},{"runtime":"python:3.12-alpine","exit_code":1},{"runtime":"python:3.12-slim","exit_code":1},{"runtime":"python:3.13-alpine","exit_code":1},{"runtime":"python:3.13-slim","exit_code":1},{"runtime":"python:3.9-alpine","exit_code":1},{"runtime":"python:3.9-slim","exit_code":1}]},"compatibility":{"tag":"verified","tag_description":"installs cleanly on critical runtimes, fast import, recently 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