python 中的时间模块time
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(),time.localtime()
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()
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 201100:29:41'
>>> strftime("%a %d %b %Y%H:%M:%S", gmtime())
'Wed 02 Mar 201116:30:09'
>>> 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
2
tm_mday
range
3
tm_hour
range
4
tm_min
range
5
tm_sec
range ; see (1) in strftime()description
6
tm_wday
range , Monday is 0
7
tm_yday
range
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 .
%H
Hour (24-hour clock) as a decimal number .
%I
Hour (12-hour clock) as a decimal number .
%j
Day of the year as a decimal number .
%m
Month as a decimal number .
%M
Minute as a decimal number .
%p
Locale’s equivalent of either AM or PM.
(1)
%S
Second as a decimal number .
(2)
%U
Week number of the year (Sunday as the first day of the week) as a decimal number . All days in a new year preceding the first Sunday are considered to be in week 0.
(3)
%w
Weekday as a decimal number .
%W
Week number of the year (Monday as the first day of the week) as a decimal number . 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 .
%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
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