partial_schema_factory.py

from copy import deepcopy

from marshmallow import Schema, fields

def PartialSchemaFactory(schema_cls):
    schema = schema_cls(partial=True)
    for field_name, field in schema.fields.items():
        if isinstance(field, fields.Nested):
            new_field = deepcopy(field)
            new_field.schema.partial = True
            schema.fields[field_name] = new_field
    return schema

class Address(Schema):
    street = fields.Str(required=True)
    city = fields.Str(required=True)
    state = fields.Str(required=True)
    zipcode = fields.Str(required=True)
    country = fields.Str(required=True)

class User(Schema):
    first_name = fields.Str(required=True)
    last_name = fields.Str(required=True)
    address = fields.Nested(Address)

payload = {
    'first_name': 'John',
    'address': {
        'zipcode': '90210'
    }
}

user_schema = PartialSchemaFactory(User)
data, errors = user_schema.load(payload)
assert errors == {}