Marshmallow

4.2.3 · active · verified Sat Mar 28

Marshmallow is a lightweight library for converting complex datatypes to and from native Python datatypes. The current version is 4.2.3, released on March 28, 2026. It follows a regular release cadence, with updates approximately every few months.

Warnings

breaking In Marshmallow 4.x, the 'load' method now returns a dictionary instead of an OrderedDict by default. To maintain the previous behavior, set the 'ordered' option to True in the schema's Meta class.
Fix: Add 'ordered = True' in the Meta class of your schema.
gotcha The 'load' method in Marshmallow 4.x raises a ValidationError if it encounters unknown fields by default. To change this behavior, set the 'unknown' option in the schema's Meta class.
Fix: Add 'unknown = INCLUDE' in the Meta class of your schema to include unknown fields.

Install

pip install marshmallow Install Marshmallow

Imports

Schema
```
from marshmallow import Schema
```
Ensure correct import path to avoid ImportError.
fields
```
from marshmallow import fields
```
Import fields from marshmallow to access various field types.

Quickstart

A simple example demonstrating how to define a schema and load data using Marshmallow.

from marshmallow import Schema, fields

class UserSchema(Schema):
    name = fields.Str()
    email = fields.Email()
    created_at = fields.DateTime()

user_data = {
    'name': 'Monty',
    'email': 'monty@python.org',
    'created_at': '2014-08-17T14:54:16.049594+00:00'
}

schema = UserSchema()
result = schema.load(user_data)
print(result)

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