python中datetime的常用功能

datetime在python中比较常用，主要用来处理时间日期，使用前先倒入datetime模块，下面总结一下本人用到的常用功能。

1.当前时间

In [30]: datetime.datetime.now()
Out[30]: datetime.datetime(2018, 9, 11, 10, 40, 30, 190295)

2.当前日期

In [32]: datetime.datetime.now().date()
Out[32]: datetime.date(2018, 9, 11)

3.当前时间tuple

In [35]: datetime.datetime.now().timetuple()
Out[35]: time.struct_time(tm_year=2018, tm_mon=9, tm_mday=11, tm_hour=10, tm_min=44, tm_sec=35, tm_wday=1, tm_yday=254, tm_isdst=-1)

4.时间移动（几天、几小时前后...）

使用datetime.timedelta这个方法来前后移动时间，可以用的参数有weeks，days，hours，minutes，seconds，microseconds。

>>> print datetime.datetime.now() + datetime.timedelta(days=1)
2015-07-18 16:49:48.574000
>>> print datetime.datetime.now() + datetime.timedelta(hours=1)
2015-07-17 17:49:57.122000
>>> print datetime.datetime.now() + datetime.timedelta(minutes=-30)
2015-07-17 16:20:08.619000

上个月最后一天

>>> print datetime.date(day=1,month=datetime.date.today().month,year=datetime.date.today().year) - datetime.timedelta(days=1)

2015-06-30

自然月的时间移动

https://dateutil.readthedocs.io/en/stable/relativedelta.html

In [13]: import datetime

In [14]: from dateutil.relativedelta import relativedelta

In [15]: a = datetime.datetime(2018,8,31)

In [16]: b = a - relativedelta(months=+6)

In [17]: a
Out[17]: datetime.datetime(2018, 8, 31, 0, 0)

In [18]: b
Out[18]: datetime.datetime(2018, 2, 28, 0, 0)

5.获取两个时间的时间差

>>> (datetime.datetime.now() - datetime.datetime.utcnow()).total_seconds()
28800.0

6.时间转化

datetime转str格式：

>>> datetime.datetime.now().strftime("%Y-%m-%d %H:%M:%S")
'2015-07-17 16:58:46'

str格式转datetime格式：

>>> datetime.datetime.strptime("2015-07-17 16:58:46","%Y-%m-%d %H:%M:%S")
datetime.datetime(2015, 7, 17, 16, 58, 46)
>>> print datetime.datetime.strptime("2015-07-17 16:58:46","%Y-%m-%d %H:%M:%S")
2015-07-17 16:58:46
>>> print type(datetime.datetime.strptime("2015-07-17 16:58:46","%Y-%m-%d %H:%M:%S"))
<type 'datetime.datetime'>

datetime转timestamp：

 time
>>> now=datetime.datetime.now()
>>> time.mktime(now.timetuple())
1437123812.0

timestamp转datetime:

>>> datetime.datetime.fromtimestamp(1437123812.0)
datetime.datetime(2015, 7, 17, 17, 3, 32)
>>> print datetime.datetime.fromtimestamp(1437123812.0)
2015-07-17 17:03:32