Python 时间序列化方法

import datetime
import json
from datetime import date

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


d = datetime.datetime.now()
d1 = date.today()
print json.dumps(d, cls=DateTimeEncoder)
print json.dumps(d1,cls=DateTimeEncoder)

解决以下问题：

raise TypeError(repr(o) + " is not JSON serializable")
TypeError: datetime.datetime(2017, 2, 28, 18, 22, 9, 955000) is not JSON serializable