Previously I used the marshmallow library with the Flask. Some time ago I have tried FastAPI with Pydantic. At first glance pydantic seems similar to masrhmallow but on closer inspection they differ. And for me the main difference between them is post_load methods which are from marshmallow. I can't find any analogs for it in pydantic. post_load is decorator for post-processing methods. Using it I can handle return object on my own, can do whatever I want: class ProductSchema(Schema): alias = fields.Str() category = fields.Str() brand = fields.Str() @post_load def check_alias(self, params, **kwargs): """One of the fields must be filled""" if not any([params.get('alias'), params.get('category'), params.get('brand')]): raise ValidationError('No alias provided', field='alias') return params Besides it used not only for validation. Code example is just for visual understanding, do not analyze it, I have just invented it. So my question is: is there any analog for post_load in pydantic? Continue reading...
