python 中的时间模块time

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　　在Django的学习过程中的时间处理过程中遇到了strftime函数，于是结合《python cookbook》和python docs 对time模块中常用的一些操作和函数做了一点总结和归纳。

• time.time()
  

　　
　　代表了从特定时间点，也被称作纪元（epoch：[英] [?i:p?k] [美] [??p?k, ?i?pɑk] ）开始所经历的秒数，是一个看起来不够直观的浮点数，这个时间根据不同的平台有所不同，一般为1970年1月1日午夜。例：




>>> import time

>>> time.time()
1299080804.953

>>> print time.asctime(time.gmtime(0))
Thu Jan 01 00:00:00 1970

• time.gmtime([secs]),  time.localtime([secs])
  

　　time.gmtime将任何时间戳（参数secs所代表的秒数）转化为一个元组，该元组为GMT（格林威治标准时），亦即UTC（世界标准时间）。也可以传递一个时间戳（从纪元开始经历的秒数）给time.localtime，会根据当前时区进行时间转化。




>>> time.gmtime(0)
time.struct_time(tm_year=1970, tm_mon=1, tm_mday=1, tm_hour=0, tm_min=0, tm_sec=0, tm_wday=3, tm_yday=1, tm_isdst=0)
>>> time.localtime(0)
time.struct_time(tm_year=1970, tm_mon=1, tm_mday=1, tm_hour=8, tm_min=0, tm_sec=0, tm_wday=3, tm_yday=1, tm_isdst=0)

• time.asctime([t])
  

　　将struct_time转换为一个由24字符组成的字符串（24-character string），格式如：
　　




Thu Mar 03 00:16:04 2011

• time.strftime(format[, t])
  

　　将一个元组（tuple）或者struct_time类，即参数t，转换为指定格式的字符串

• time.striptime(string[, format])
  

　　跟time.strftime相反的操作，解析给定的字符串并返回一个struct_time类。例：





>>> from time import strftime, gmtime

>>> strftime("%a %d %b %Y  %H:%M:%S")
'Thu 03 Mar 2011  00:29:41'
>>> strftime("%a %d %b %Y  %H:%M:%S", gmtime())
'Wed 02 Mar 2011  16:30:09'
>>> time.strptime("30 Feb 11", "%d %b %y")
...
ValueError: day is out of range for month
>>> time.strptime("28 Feb 11", "%d %b %y")
time.struct_time(tm_year=2011, tm_mon=2, tm_mday=28, tm_hour=0, tm_min=0, tm_sec=0, tm_wday=0, tm_yday=59, tm_isdst=-1)

• time.sleep(secs)
  

　　 可以实现在python程序中的延时，单位为秒，并支持浮点数非整数秒的延时。例：




>>> for i in range(3):
    time.sleep(2.5)
    print "hello world!"
   
hello world!
hello world!
hello world!
>>>
　　
附一：struct_time


IndexAttributeValues




0
tm_year
(for example, 1993)


1
tm_mon
range [1, 12]


2
tm_mday
range [1, 31]


3
tm_hour
range [0, 23]


4
tm_min
range [0, 59]


5
tm_sec
range [0, 61]; see (1) in strftime()description


6
tm_wday
range [0, 6], Monday is 0


7
tm_yday
range [1, 366]


8
tm_isdst
0, 1 or -1; see below
　　附二：directives can be embedded in the format string


DirectiveMeaningNotes




%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.



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



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



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



%j
Day of the year as a decimal number [001,366].



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



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



%p
Locale’s equivalent of either AM or PM.
(1)


%S
Second as a decimal number [00,61].
(2)


%U
Week number of the year (Sunday as the first day of the week) as a decimal number [00,53]. All days in a new year preceding the first Sunday are considered to be in week 0.
(3)


%w
Weekday as a decimal number [0(Sunday),6].



%W
Week number of the year (Monday as the first day of the week) as a decimal number [00,53]. All days in a new year preceding the first Monday are considered to be in week 0.
(3)


%x
Locale’s appropriate date representation.



%X
Locale’s appropriate time representation.



%y
Year without century as a decimal number [00,99].



%Y
Year with century as a decimal number.



%Z
Time zone name (no characters if no time zone exists).



%%
A literal '%' character.
　　
　　参考：1. python cookbook
　　        2. docs：http://docs.python.org/library/time.html#time.struct_time