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# Python Time Conversion #
##########################
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-- 一. 时间的表示类型 --
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py中可能涉及的time有四种类型
    1. time string
    2. datetime
tuple(datetime obj)
    3. time tuple(time
obj)
    4. timestamp
1. time string
string是最简单的表示time的方式
如如下代码生成的即为string
   
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>>> time.ctime()
    'Mon Dec 17 21:02:55
2012'
   
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或者更简单的生成一个字符串
   
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    time_string =
'2000-01-02 03:04:05'
   
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2. datetime tuple(datetime obj)
datetime tuple是datetime.datetime对象类型
   
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>>>
datetime.now()
    datetime.datetime(2012,
12, 17, 21, 3, 44, 139715)
   
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3. time tuple(time obj)
time tuple是time.struct_time对象类型
   
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time.struct_time(tm_year=2008, tm_mon=11, tm_mday=10, tm_hour=17,
tm_min=53, tm_sec=59, tm_wday=0, tm_yday=315, tm_isdst=-1)
   
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4. timestamp
时间戳类型:自1970年1月1日(00:00:00 GMT)以来的秒数
   
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>>> time.time()
    1355749338.05917
   
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-- 二. 类型之间的转换 --
------------------------
1. string 转换为其它
初始化:
    date_str = "2008-11-10
17:53:59"
1.1 string --> datetime obj
导入:
    import datetime
   
datetime.datetime.strptime(string, format)
eg
   
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>>> dt_obj =
datetime.datetime.strptime(date_str, "%Y-%m-%d %H:%M:%S")
   
>>> dt_obj
    datetime.datetime(2008,
11, 10, 17, 53, 59)
   
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1.2 string --> time obj
导入:
    import time
    time.strptime(string,
format)
eg
   
----------------------------------------------
   
#time模块有类似datetime中的strptime()函数
   
>>> date_str =
"2008-11-10 17:53:59"
   
>>> t_obj =
time.strptime(date_str, "%Y-%m-%d %H:%M:%S")
   
>>> t_obj
   
time.struct_time(tm_year=2008, tm_mon=11, tm_mday=10, tm_hour=17,
tm_min=53, tm_sec=59, tm_wday=0, tm_yday=315, tm_isdst=-1)
   
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2. datetime obj转换为其它
datetime obj转换为其它类型,用的都是datetime的函数
初始化:
    dt_obj =
datetime.datetime(2008, 11, 10, 17, 53, 59)
2.1 dt obj --> string
   
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    date_str =
dt_obj.strftime("%Y-%m-%d %H:%M:%S")
   
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2.2 dt obj --> time obj
   
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    time_tuple =
dt_obj.timetuple()
   
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3. time obj转换为其它
初始化:
    time_tuple = (2008, 11,
12, 13, 51, 18, 2, 317, 0)
3.1 time obj --> string
   
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    date_str =
time.strftime("%Y-%m-%d %H:%M:%S", time_tuple)
   
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3.2 time obj --> datetime obj
   
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datetime.datetime(*time_tuple[0:6])
   
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3.3 time obj --> timestamp
   
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    ts =
time.mktime(time_tuple)
   
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4. timestamp转换为其它
初始化:
    timestamp =
1226527167.595983
--!!--注意以下两种都使用local时区
4.1 timestamp --> dt obj
   
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    dt_obj =
datetime.fromtimestamp(timestamp)
   
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4.2 timestamp --> time obj
   
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    time_tuple =
time.localtime(timestamp)
   
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--!!--以下两种方式和时区相关,比较标准时区时间和本地时区时间
4.3 使用UTC --> dt obj
   
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    #本地时区时间
   
>>>
datetime.datetime.fromtimestamp(tm)
    datetime.datetime(2012,
12, 17, 23, 39, 58, 401881)
    #标准时区时间
   
>>>
datetime.datetime.utcfromtimestamp(tm)
    datetime.datetime(2012,
12, 17, 15, 39, 58, 401881)
   
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4.4 使用UTC --> time obj
   
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    #本地时区时间
   
>>>
time.localtime(tm)
   
time.struct_time(tm_year=2012, tm_mon=12, tm_mday=17, tm_hour=23,
tm_min=39, tm_sec=58, tm_wday=0, tm_yday=352, tm_isdst=0)
    #标准时区时间
   
>>>
time.gmtime(tm)
   
time.struct_time(tm_year=2012, tm_mon=12, tm_mday=17, tm_hour=15,
tm_min=39, tm_sec=58, tm_wday=0, tm_yday=352, tm_isdst=0)
   
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