Python之time模塊

time.strptime()：將普通字符時間轉換爲時間元祖，注意這兩者在轉換時需要指定字符時間的格式（%Y%m%d這裏只用到了年月日）

import time
print time.strptime('20170301', '%Y%m%d')

輸出結果：

time.struct_time(tm_year=2017, tm_mon=3, tm_mday=1, tm_hour=0, tm_min=0, tm_sec=0, tm_wday=2, tm_yday=60, tm_isdst=-1)

time.mktime()：將上一步的時間元祖轉換爲時間戳，即1970年0時0分0秒到20170301的0時0分0秒爲止，過了多少秒

import time
print time.mktime(time.strptime('20170301','%Y%m%d'))

輸出結果：

1488297600.0

time.localtime():將時間戳轉換爲時間元祖

import time
print time.localtime(1488297600.0)

輸出結果：

time.struct_time(tm_year=2017, tm_mon=3, tm_mday=1, tm_hour=0, tm_min=0, tm_sec=0, tm_wday=2, tm_yday=60, tm_isdst=0)

time.strftime：將時間元祖復原爲普通字符時間，同樣注意需要指定字符時間的格式

import time
print time.strftime('%Y%m%d',time.localtime(1488297600.0))

輸出結果：

20170301

求當前時間：datetime.now()

from datetime import datetime, timedelta
print datetime.now()
print (datetime.now()).strftime('%Y%m%d')
print (datetime.now()).strftime('%Y/%m/%d %H:%M:%S')

輸出結果：

2017-03-01 09:48:23.104000
20170301
2017/03/01 09:48:23

時間運算：timedelta(weeks, days, hours, second, milliseconds, microseconds) ，參數可選，默認爲0

from datetime import datetime, timedelta
print (datetime.now()-timedelta(days=1)).strftime('%Y%m%d')  # 1天前的日期
print (datetime.now()+timedelta(days=100)).strftime('%Y%m%d') # 100天后的日期
print (datetime.now()-timedelta(hours=1)).strftime('%Y/%m/%d %H:%M:%S')      #求一小時前的時間

輸出結果：

20170228201706092017/03/01 08:42:45

字符時間常用格式：

%Y  Year with century as a decimal number.  

%m  Month as a decimal number [01,12].     

%d  Day of the month as a decimal number [01,31].  

%H  Hour (24-hour clock) as a decimal number [00,23].  

%M  Minute as a decimal number [00,59].

%S  Second as a decimal number [00,59].  

%z  Time zone offset from UTC.    

%a  Locale's abbreviated weekday name. 

%A  Locale's full weekday name. 

%b  Locale's abbreviated month name.  

%B  Locale's full month name.   

%c  Locale's appropriate date and time representation. 

%I  Hour (12-hour clock) as a decimal number [01,12]. 

%p  Locale's equivalent of either AM or PM.

from datetime import datetime
print (datetime.now()).strftime('%Y')
print (datetime.now()).strftime('%m')
print (datetime.now()).strftime('%d')
print (datetime.now()).strftime('%H')
print (datetime.now()).strftime('%M')
print (datetime.now()).strftime('%S')
print (datetime.now()).strftime('%a')
print (datetime.now()).strftime('%A')
print (datetime.now()).strftime('%b')
print (datetime.now()).strftime('%B')
print (datetime.now()).strftime('%c')
print (datetime.now()).strftime('%I')
print (datetime.now()).strftime('%p')

輸出結果：

2017
03
01
09
56
30

Wed
Wednesday
Mar
March
03/01/17 09:56:30
09
AM