Marshmallow Invalid input type on nesting

Question

I wrote a nested schema. but whenever i pass the json from postman it shows invalid input type. here is the code below:

class ChalanProductsSchema(Schema):
   product_id = fields.Str(required=True)


class ChalanDetailsSchema(Schema):
    chalan_id = fields.Str(required=True)
    rows = fields.Nested(ChalanProductsSchema, many=True)


   chalan_details_Schema = ChalanDetailsSchema(many=True)

# serializing json
data = chalan_details_Schema.load(json_data)


#json i pass from postman
{
"chalan_id":"2022.08.0002",
"rows":[
     {
       "product_id":"XXXXXXXX1"
     },
     {
       "product_id":"XXXXXXXX2"
     }
    ]
 }

Error I am having:

{ "_schema": [ "Invalid input type." ] }

Answer 1

Looks like you don't expect multiple ChalanDetail

Try to change

chalan_details_Schema = ChalanDetailsSchema(many=True)

into

chalan_details_Schema = ChalanDetailsSchema()