1.str转换为datetime
>>> from datetime import datetime
>>> cday = datetime.strptime('2015-6-1 18:19:59', '%Y-%m-%d %H:%M:%S')
>>> print(cday)
2015-06-01 18:19:59
2.datetime转换为str
>>> from datetime import datetime
>>> now = datetime.now()
>>> print(now.strftime('%a, %b %d %H:%M'))
Mon, May 05 16:28