python 将字符串类型转为时间类型

import datetime,time
stringDate = "2006-05-18 19:35:00"
dt = datetime.datetime.fromtimestamp(time.mktime(time.strptime(stringDate,"%Y-%m-%d %H:%M:%S")))
print dt
2006-05-18 19:35:00
>>> print type(dt)
<type 'datetime.datetime'>
>>>
import datetime,time
stringDate = "2006-05-