Custom error messages

To customize the schema-level error messages that load <marshmallow.Schema.load> and loads <marshmallow.Schema.loads> use when raising a ValidationError <marshmallow.exceptions.ValidationError>, override the error_messages <marshmallow.Schema.error_messages> class variable:

.. code-block:: python

class MySchema(Schema):
    error_messages = {
        "unknown": "Custom unknown field error message.",
        "type": "Custom invalid type error message.",
    }

Field-level error message defaults can be set on Field.default_error_messages <marshmallow.fields.Field.default_error_messages>.

.. code-block:: python

from marshmallow import Schema, fields

fields.Field.default_error_messages["required"] = "You missed something!"

class ArtistSchema(Schema): name = fields.Str(required=True) label = fields.Str(required=True, error_messages={"required": "Label missing."})

print(ArtistSchema().validate({}))

{'label': ['Label missing.'], 'name': ['You missed something!']}