让python json encode datetime类型

import json 
from datetime import date, datetime 
def __default(obj): 
if isinstance(obj, datetime): 
return obj.strftime('%Y-%m-%dT%H:%M:%S') 
elif isinstance(obj, date): 
return obj.strftime('%Y-%m-%d') 
else: 
raise TypeError('%r is not JSON serializable' % obj) 

print json.dumps({'d': datetime.now(), 'today': date.today(), 'x': 111}, 
default=__default)