python datetime的加减操作

python时间操作有很多，今天根据业务需求需要做时间的加减操作，找了很久没找到。在此记录，以防忘记

from datetime import timedelta

timedelta可以做时间的加减操作

一下是官方的解释

class datetime.timedelta([days[, seconds[, microseconds[, milliseconds[, minutes[, hours[, weeks]]]]]]])
All arguments are optional and default to 0. Arguments may be ints, longs, or floats, and may be positive or negative.

Only days, seconds and microseconds are stored internally. Arguments are converted to those units:

A millisecond is converted to 1000 microseconds.
A minute is converted to 60 seconds.
An hour is converted to 3600 seconds.
A week is converted to 7 days.
and days, seconds and microseconds are then normalized so that the representation is unique, with

0 <= microseconds < 1000000
0 <= seconds < 3600*24 (the number of seconds in one day)
-999999999 <= days <= 999999999
If any argument is a float and there are fractional microseconds, the fractional microseconds left over from all arguments are combined and their sum is rounded to the nearest microsecond. If no argument is a float, the conversion and normalization processes are exact (no information is lost).

If the normalized value of days lies outside the indicated range, OverflowError is raised.

Note that normalization of negative values may be surprising at first. For example,

>>> from datetime import timedelta
>>> d = timedelta(microseconds=-1)
>>> (d.days, d.seconds, d.microseconds)
(-1, 86399, 999999)

具体用法：

time = timedelta(minutes=1)

datetime.now +  time 

minutes处可以填写单位，后边关联的是具体的时间，然后和你需要的时间直接进行加减操作