关于python json datatime报错解决办法

错误 datetimeTypeError: datetime.datetime(2017, 3, 21, 2, 11, 21) is not JSON serializable

class DateEncoder(json.JSONEncoder):
    def default(self, obj):
        if isinstance(obj,datetime.datetime):
            return obj.strftime("%Y-%m-%d %H:%M:%S")
        else:
            return json.JSONEncoder.default(self, obj)

datetime_s = datetime.datetime(2019, 8, 14, 12, 24, 10, 248000)
print(datetime_s)
print(type(datetime_s))
json_datetime = json.dumps(datetime_s, cls=DateEncoder)
print(json_datetime)