python datetime相减

>>> a=datetime.datetime(2012, 3, 10, 8, 40, 50, 737418)
>>> b=datetime.datetime(2012, 3, 9, 8, 40, 50, 737418)
>>> a-b
datetime.timedelta(1)
>>> c=a-b
>>> c.days
1
>>> c.seconds
0
>>> a=datetime.datetime(2012, 2, 10, 8, 40, 50, 737418)
>>> b=datetime.datetime(2012, 3, 9, 8, 40, 50, 737418)
>>> b-a
datetime.timedelta(28)
>>> c=b-a
>>> c.days
28
>>> b=datetime.datetime(2012, 3, 9, 7, 40, 50, 737418)
>>> b-a
datetime.timedelta(27, 82800)
>>> c=b-a
>>> c.days
27
>>> c.seconds
82800
>>> a=datetime.datetime(2012, 2, 10, 8, 40, 50, 737410)
>>> b=datetime.datetime(2012, 3, 9, 7, 40, 50, 737428)
>>> c=b-a
>>> c
datetime.timedelta(27, 82800, 18)
>>> a=datetime.datetime(2011, 2, 10, 8, 40, 50, 737410)
>>> b=datetime.datetime(2012, 3, 9, 7, 40, 50, 737428)
>>> c=b-a
>>> c
datetime.timedelta(392, 82800, 18)