python 日期循環

import datetime
start='2016-06-01'
end='2017-01-01'
 
datestart=datetime.datetime.strptime(start,'%Y-%m-%d')
dateend=datetime.datetime.strptime(end,'%Y-%m-%d')
 
while datestart<dateend:
    datestart+=datetime.timedelta(days=1)
    print datestart.strftime('%Y-%m-%d')