Registry / serialization / marshmallow-jsonschema

marshmallow-jsonschema

library0.16.0pypypi✓ verified 22d ago

marshmallow-jsonschema translates marshmallow schemas into JSON Schema Draft v7 compliant jsonschema. It enables developers to generate JSON Schemas directly from their existing Marshmallow schemas, which is particularly useful for frontend form generation, API documentation, or validation in other systems. The current version is 0.13.0, released in October 2021, suggesting a maintenance rather than a rapid release cadence.

serialization

pip install marshmallow-jsonschema

github ↗package ↗

INSTALL

IMPORT

SIG · MARSHMALLOW-JSONSC

marshmallow-jsonschema

serializationpythonv0.16.0

Install

1.7s avg

Import

615ms

Disk

17MB

Pass rate

10/ 10

Env Coverage10 / 10

glibc

3.9–3.13

musl

3.9–3.13

Install & Compatibility

Where this runs

tested against v0.16.0 · 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

py 3.10–3.95 runs

installs and imports cleanly · install 0.0s · import 0.620s · 18.9MB

glibc

py 3.10–3.95 runs

installs and imports cleanly · install 1.7s · import 0.610s · 19MB

17MB installed

● package 17MB

Code

Verified usage

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

JSONSchema

✓ from marshmallow_jsonschema import JSONSchema

This quickstart demonstrates how to define a basic Marshmallow schema and then use `marshmallow-jsonschema` to convert it into a JSON Schema representation. The output is a standard JSON Schema dictionary, ready for use in other applications.

from marshmallow import Schema, fields from marshmallow_jsonschema import JSONSchema class UserSchema(Schema): username = fields.String(required=True, metadata={'description': 'The user\'s unique identifier'}) age = fields.Integer(required=False, allow_none=True, metadata={'minimum': 0}) email = fields.Email(required=True) # Instantiate the JSONSchema converter json_schema_converter = JSONSchema() # Convert your Marshmallow schema to a JSON Schema dictionary user_json_schema = json_schema_converter.dump(UserSchema()) import json print(json.dumps(user_json_schema, indent=2))

Debug

Known issues

breaking`marshmallow-jsonschema` is not compatible with `marshmallow.fields.Enum` introduced in Marshmallow v3.18.0. Using this field type will result in an `UnsupportedValueError`.

fix

Avoid using `marshmallow.fields.Enum` or consider using the `marshmallow-jsonschema-3` fork which addresses this and other OpenAPI/JSON Schema 3.x features. Alternatively, implement custom field handling for enums.

affects: marshmallow-jsonschema < 0.14.0 with marshmallow >= 3.18.0

deprecatedWhen used with newer Marshmallow versions (e.g., v4.x), `marshmallow-jsonschema` may produce `RemovedInMarshmallow4Warning` warnings related to deprecated field attributes like `default` (use `dump_default`) and passing field `metadata` as keyword arguments (use explicit `metadata=` argument).

fix

These are warnings from Marshmallow itself, not `marshmallow-jsonschema`. While the library might still function, upgrading `marshmallow-jsonschema` to a version that properly supports Marshmallow 4.x is the long-term solution. For now, ensure your Marshmallow schemas follow the latest best practices for field definition.

affects: marshmallow-jsonschema < 0.14.0 with marshmallow >= 4.0.0

gotcha`marshmallow-jsonschema` only supports converting Marshmallow schemas *to* JSON Schema. There is no built-in functionality to generate a Marshmallow schema *from* an existing JSON Schema.

fix

If you need to generate Marshmallow schemas from JSON Schema, you will need to use a different tool or implement a custom solution. This library is strictly a one-way conversion tool.

affects: All versions

Errors

Common errors & fixes

marshmallow_jsonschema.exceptions.UnsupportedValueError: unsupported field type <fields.Enum(...)>

marshmallow-jsonschema version 0.13.0 does not natively support the `marshmallow.fields.Enum` field type, particularly when used with Marshmallow versions 3.18.0 or higher.

fix

Avoid using `marshmallow.fields.Enum` directly. Instead, implement a custom field with a `_jsonschema_type_mapping` method, or consider using the `marshmallow-jsonschema-3` fork which provides updated compatibility.

RemovedInMarshmallow4Warning

This warning occurs when marshmallow-jsonschema 0.13.0 is used with Marshmallow 4.x, as the library's fixed version uses deprecated attributes or patterns from older Marshmallow versions.

fix

While marshmallow-jsonschema 0.13.0 might still function, the long-term solution is to use a `marshmallow-jsonschema` version that officially supports Marshmallow 4.x (if one becomes available). Alternatively, pin your `marshmallow` dependency to a version less than 4.0.

ModuleNotFoundError: No module named 'jsonschema.compat'

The `jsonschema` library, a dependency of `marshmallow-jsonschema`, removed the `jsonschema.compat` module in its 4.0 release. If `marshmallow-jsonschema` or another library relies on this removed module, this error will occur when `jsonschema` version 4.0 or higher is installed.

fix

Pin your `jsonschema` dependency to a version less than 4.0 by running `pip install 'jsonschema<4.0'`.

ModuleNotFoundError: No module named 'marshmallow_jsonschema'

The `marshmallow-jsonschema` package is not installed in your Python environment, or the environment where the code is being run does not have access to the installed package.

fix

Install the library using pip: `pip install marshmallow-jsonschema`. Ensure you are installing it into the correct Python environment.

Upgrade

Version history

0.16.0latest on PyPI · released Apr 26, 2026

Audit

Dependencies

marshmallowrequiredCore dependency for defining schemas to be converted.

Agent activity

3 hits · last 30 days

node

Resources

githubhttps://github.com/fuhrysteve/marshmallow-jsonschema ↗

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