Define fields programmatically in Marshmallow Schema

Question

Say I have a Schema like this:

class MySchema(Schema):

    field_1 = Float()
    field_2 = Float()
    ...
    field_42 = Float()

Is there a w

Answer 1

All you need to do is to use type() function to build your class with any attributes you want:

MySchema = type('MySchema', (marshmallow.Schema,), {
    attr: marshmallow.fields.Float()
    for attr in FIELDS
})

You can even have different types of fields there:

fields = {}
fields['foo'] = marshmallow.fields.Float()
fields['bar'] = marshmallow.fields.String()
MySchema = type('MySchema', (marshmallow.Schema,), fields)

or as a base for your customizations:

class MySchema(type('_MySchema', (marshmallow.Schema,), fields)):
    @marshmallow.post_dump
    def update_something(self, data):
        pass