python json dumps datetime类型报错

# -*- coding: utf-8 -*-

import json
from datetime import date, datetime

class MyEncoder(json.JSONEncoder):
    def default(self, obj):
        # if isinstance(obj, datetime.datetime):
        #     return int(mktime(obj.timetuple()))
        if isinstance(obj, datetime):
            return obj.strftime('%Y-%m-%d %H:%M:%S')
        elif isinstance(obj, date):
            return obj.strftime('%Y-%m-%d')
        else:
            return json.JSONEncoder.default(self, obj)

　　# 使用方式
    # print(json.dumps(dataMap, cls=MyEncoder))