python json模塊默認不能序列化decimal和datetime數據，可以通過自定義一個序列化的類實現：

link: http://www.cnblogs.com/buxizhizhoum/p/7607036.html

import json
import datetime


class SupplementaryEncoder(json.JSONEncoder):
    def default(self, obj):
        if isinstance(obj, decimal.Decimal):  # for decimal
            return float(obj)
        
 
elif isinstance(obj, datetime.datetime):  # for datetime
            return obj.strftime("%Y-%m-%d %H:%M:%S")
        return json.JSONEncoder.default(self, obj)

test_dict = {"a": datetime.datetime.now()}
res = json.dumps(test_dict, cls=SupplementaryEncoder)

json decimal and datetime