Python 时间获取

摘自：http://www.jb51.net/article/91365.htm

摘自：https://www.cnblogs.com/liuq/p/6211005.html

一、在python中，除了time模块外还有datetime模块，也可以方便的操作时间，比如用datetime模块来显示当前时间

>>> from datetime import datetime

>>> datetime.now().strftime('%Y-%m-%d %H:%M:%S')

'2016-07-21 19:49:15'

>>> datetime.now().isoformat()

'2016-07-21T19:56:46.744893'

>>> str(datetime.now())

'2016-07-21 19:48:37.436886'

二、时间差

1. 时间字符串 --> 时间戳

    1） time 模块

timestring = '2016-12-21 10:22:56'
print time.mktime(time.strptime(timestring, '%Y-%m-%d %H:%M:%S')) # 1482286976.0

    time.mktime() 与 time.localtime() 互为还原函数。

    time.mktime(timetuple) ：将时间元组转换成时间戳

    time.localtime([timestamp])：将时间戳转会为时间元组

    2） datetime 模块

在这里没有找到，似乎只有 time 模块能获取时间戳

2. 时间戳 --> 时间字符串

    1） time 模块

timestamp = time.time()
timestruct = time.localtime(timestamp)
print time.strftime('%Y-%m-%d %H:%M:%S', timestruct) # 2016-12-22 10:49:57

    2） datetime 模块

import datetime
timestamp = 1482374997.55
datetime_struct = datetime.datetime.fromtimestamp(timestamp)
print datetime_struct.strftime('%Y-%m-%d %H:%M:%S') # 2016-12-22 10:49:57

datetime_struct = datetime.datetime.utcfromtimestamp(timestamp)
print datetime_struct.strftime('%Y-%m-%d %H:%M:%S') # 2016-12-22 02:49:57

    fromtimestamp(timestamp[, tz])：将时间戳转为当地的时间元组
    utcfromtimestamp(timestamp)：将时间戳转为UTC的时间元组。以北京为例：utc时间比北京当地时间少8个小时。

3. 时间差计算

    1） 几天/周前

import datetime

now = datetime.datetime.now()
three_days_ago = now + datetime.timedelta(days=-3)
three_weeks_ago = now + datetime.timedelta(weeks=-3)

print now # datetime.datetime(2016, 12, 22, 11, 24, 49, 987171)
print three_days_ago # datetime.datetime(2016, 12, 19, 11, 24, 49, 987171)
print three_weeks_ago # datetime.datetime(2016, 12, 1, 11, 24, 49, 987171)

    2） 几天/周后

import datetime

now = datetime.datetime.now()
three_days_later = now + datetime.timedelta(days=3)
three_weeks_later = now + datetime.timedelta(weeks=3)

print now # datetime.datetime(2016, 12, 22, 11, 24, 49, 987171)
print three_days_later # datetime.datetime(2016, 12, 25, 11, 24, 49, 987171)
print three_weeks_later # datetime.datetime(2017, 1, 12, 11, 24, 49, 987171)

注意：没有months和years

    3）时间差

import time
import datetime

start = datetime.datetime.now()
time.sleep(30)
end = datetime.datetime.now()

print (end-start).days # 0 天数
print (end-start).total_seconds() # 30.029522 精确秒数
print (end-start).seconds # 30 秒数
print (end-start).microseconds # 29522 毫秒数

注意：没有分钟

4. 任意时间字符串转换时间对象

import time
from dateutil import parser
 
time_string = time.ctime() # 'Thu Dec 22 10:35:25 2016'，这里可以是任意的时间格式
datetime_struct = parser.parse(time_string)
print type(datetime_struct) # <type 'datetime.datetime'>
print datetime_struct.strftime('%Y-%m-%d %H:%M:%S') # 2016-12-22 13:58:59

三、显示距离当前时间的n天

today = datetime.date.today()
yesterday = today - datetime.timedelta(days=10)
today = today - datetime.timedelta(days=0)
date_from = str(yesterday)+' 00:00:00'
date_till = str(today)+' 23:59:59'
unix_from = int(time.mktime(time.strptime(date_from, '%Y-%m-%d %H:%M:%S')))#转换为时间戳
unix_till = int(time.mktime(time.strptime(date_till, '%Y-%m-%d %H:%M:%S')))#转换为时间戳