import json
from typing import Any

class User:
    name = "cwx"
    value = "val"
        
class MyJsonEncoder(json.JSONEncoder):
    def default(self, o: Any) -> Any:
        if isinstance(o,User):
            return {
                "name": o.name,
                "value": o.value
            }
        return super().default(o)
    
s = json.dumps(User(),cls=MyJsonEncoder,ensure_ascii=False)
print(s)