Custom error handling

By default, Schema.load <marshmallow.Schema.load> will raise a :exc:ValidationError <marshmallow.exceptions.ValidationError> if passed invalid data.

You can specify a custom error-handling function for a :class:Schema by overriding the handle_error <marshmallow.Schema.handle_error> method. The method receives the :exc:ValidationError <marshmallow.exceptions.ValidationError> and the original input data to be deserialized.

.. code-block:: python

import logging
from marshmallow import Schema, fields


class AppError(Exception):
    pass


class UserSchema(Schema):
    email = fields.Email()

    def handle_error(self, exc, data, **kwargs):
        """Log and raise our custom exception when (de)serialization fails."""
        logging.error(exc.messages)
        raise AppError("An error occurred with input: {0}".format(data))


schema = UserSchema()
schema.load({"email": "invalid-email"})  # raises AppError