Constructing MongoDB document from a dict with character code-to-integer translation
If all attributes are in item, then you can create an instance simply with:

s = ScoreDetail(**item)


This is just a guess though. Your code looks like Django, where this would work, but even though this isn't Django, I suspect this to be supported similarly.

Without a friendly framework to convert between objects and json, you could use the serialization/deserialization features of the json package, with custom serializer/deserializer implementations.