marshmallow: simplified object serialization

marshmallow is an ORM/ODM/framework-agnostic library for converting complex datatypes, such as objects, to and from native Python datatypes.

from datetime import date
from marshmallow import Schema, fields, pprint

class ArtistSchema(Schema):
    name = fields.Str()

class AlbumSchema(Schema):
    title = fields.Str()
    release_date = fields.Date()
    artist = fields.Nested(ArtistSchema())

bowie = dict(name='David Bowie')
album = dict(artist=bowie, title='Hunky Dory', release_date=date(1971, 12, 17))

schema = AlbumSchema()
result = schema.dump(album)
pprint(result.data, indent=2)
# { 'artist': {'name': 'David Bowie'},
#   'release_date': '1971-12-17',
#   'title': 'Hunky Dory'}

In short, marshmallow schemas can be used to:

• Validate input data.
• Deserialize input data to app-level objects.
• Serialize app-level objects to primitive Python types. The serialized objects can then be rendered to standard formats such as JSON for use in an HTTP API.

Get It Now

$ pip install -U marshmallow

Documentation

Full documentation is available at http://marshmallow.readthedocs.io/ .

Requirements

• Python >= 2.6 or >= 3.3

marshmallow has no external dependencies outside of the Python standard library, although python-dateutil is recommended for robust datetime deserialization.

Ecosystem

A list of marshmallow-related libraries can be found at the GitHub wiki here:

https://github.com/marshmallow-code/marshmallow/wiki/Ecosystem

Project Links

• Docs: http://marshmallow.readthedocs.io/
• Changelog: http://marshmallow.readthedocs.io/en/latest/changelog.html
• PyPI: https://pypi.python.org/pypi/marshmallow
• Issues: https://github.com/marshmallow-code/marshmallow/issues

License

MIT licensed. See the bundled LICENSE file for more details.

Changelog

2.9.1 (2016-07-21)

Bug fixes:

• Fix serialization of datetime.time objects with microseconds (464{.interpreted-text role=”issue”}). Thanks Tim-Erwin{.interpreted-text role=”user”} for reporting and thanks vuonghv{.interpreted-text role=”user”} for the fix.
• Make @validates consistent with field validator behavior: if validation fails, the field will not be included in the deserialized output (391{.interpreted-text role=”issue”}). Thanks martinstein{.interpreted-text role=”user”} for reporting and thanks @vuonghv{.interpreted-text role=”user”} for the fix.

2.9.0 (2016-07-06)

• Decimal field coerces input values to a string before deserializing to a [decimal.Decimal]{.title-ref} object in order to avoid transformation of float values under 12 significant digits (434{.interpreted-text role=”issue”}, 435{.interpreted-text role=”issue”}). Thanks davidthornton{.interpreted-text role=”user”} for the PR.

2.8.0 (2016-06-23)

Features:

• Allow only and exclude parameters to take nested fields, using dot-delimited syntax (e.g. only=['blog.author.email']) (402{.interpreted-text role=”issue”}). Thanks Tim-Erwin{.interpreted-text role=”user”} and deckar01{.interpreted-text role=”user”} for the discussion and implementation.

Support:

• Update tasks.py for compatibility with invoke>=0.13.0. Thanks deckar01{.interpreted-text role=”user”}.

2.7.3 (2016-05-05)

• Make field.parent and field.name accessible to on_bind_field (449{.interpreted-text role=”issue”}). Thanks immerrr{.interpreted-text role=”user”}.

2.7.2 (2016-04-27)

No code changes in this release. This is a reupload in order to distribute an sdist for the last hotfix release. See 443{.interpreted-text role=”issue”}.

Support:

• Update license entry in setup.py to fix RPM distributions (433{.interpreted-text role=”issue”}). Thanks rrajaravi{.interpreted-text role=”user”} for reporting.

2.7.1 (2016-04-08)

Bug fixes:

• Only add Schemas to class registry if a class name is provided. This allows Schemas to be constructed dynamically using the type constructor without getting added to the class registry (which is useful for saving memory).

2.7.0 (2016-04-04)

Features:

• Make context available to Nested field's on_bind_field method (408{.interpreted-text role=”issue”}). Thanks immerrr{.interpreted-text role=”user”} for the PR.
• Pass through user ValidationError kwargs (418{.interpreted-text role=”issue”}). Thanks russelldavies{.interpreted-text role=”user”} for helping implement this.

Other changes:

• Remove unused attributes root, parent, and name from SchemaABC (410{.interpreted-text role=”issue”}). Thanks Tim-Erwin{.interpreted-text role=”user”} for the PR.

2.6.1 (2016-03-17)

Bug fixes:

• Respect [load_from]{.title-ref} when reporting errors for nested required fields (414{.interpreted-text role=”issue”}). Thanks yumike{.interpreted-text role=”user”}.

2.6.0 (2016-02-01)

Features:

• Add partial argument to Schema.validate (379{.interpreted-text role=”issue”}). Thanks tdevelioglu{.interpreted-text role=”user”} for the PR.

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