datetime

时间转字符串

在我们的使用中，我们常常需要将时间转换为字符串，用来作为文件的名字或者用于加密字符的输出等等。例子：

from datetime import datetime 
datetime.strftime(datetime.now(),"%Y-%m-%d %H:%M:%S")

记忆方式也很简单，str from time

字符转时间

有时候我们需要将一个字符给转换为时间对象

from datetime import datetime 
>>> datetime.strptime('2018-09-09',"%Y-%m-%d")
datetime.datetime(2018, 9, 9, 0, 0)

时间戳的转换

import time 
from datetime import datetime 
stamp = time.time()
datetime.fromtimestamp(stamp)

timedelta

import datetime
print('microseconds:', datetime.timedelta(microseconds=1))
print('milliseconds:', datetime.timedelta(milliseconds=1))
print('seconds :', datetime.timedelta(seconds=1))
print('minutes :', datetime.timedelta(minutes=1))
print('hours :', datetime.timedelta(hours=1))
print('days :', datetime.timedelta(days=1))
print('weeks :', datetime.timedelta(weeks=1))

加 就是 延后几秒; 减 就是提前几秒

转换格式

Symbol	Meaning	Example
%a	Abbreviated weekday name	'Wed'
%A	Full weekday name	'Wednesday'
%w	Weekday number: 0 (Sunday) through 6 (Saturday)	'3'
%d	Day of the month (zero padded)	'13'
%b	Abbreviated month name	'Jan'
%B	Full month name	'January'
%m	Month of the year	'01'
%y	Year without century	'18'
%Y	Year with century	'2018'
%H	Hour from 24-hour clock	'17'
%I	Hour from 12-hour clock	'05'
%p	AM/PM	'PM'
%M	Minutes	'00'
%S	Seconds	'00'
%f	Microseconds	'000000'
%z	UTC offset for time zone–aware objects	'-0500'
%Z	Time zone name	'EST'
%j	Day of the year	'013'
%W	Week of the year	'02'
%c	Date and time representation for the current locale	'Wed Jan 13 17:00:00 2016'
%x	Date representation for the current locale	'01/13/16'
%X	Time representation for the current locale	'17:00:00'
%%	A literal % character	'%'

tips

工作中经常需要用到美国时间，做一个记录。 utc晚了8个小时，所以要减去即是美国时间

datetime.strftime(datetime.utcnow()-timedelta(hours=8),'%Y-%m-%d %H:%M:%S')

GMT时间格式

GMT_FORMAT =  '%a, %d %b %Y %H:%M:%S GMT'

参考

《The Python3 Standard Library By Example》