Python中用于处理日期和时间的模块包括time、datetime和calendar。在之前的推文中《Python之time模块详解》详细的介绍了time模块的相关内容，即主要处理的是时间类数据，例如时、分、秒等相关信息。今天小编将为大家介绍datetime模块的基本用法。datetime模块可处理时间、日期等数据，是date和time模块的集合，其总共定义6类：datetime.date、datetime.time、datetime.datetime、datetime.timedelta、datetime.tzinfo、datetime. timezone。tzinfo、timezone为时区类相关处理模块，本文不做过多讲解，而主要介绍前四类内容。
0. 前 言
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在开始介绍datetime模块之前，先讲一下该模块下date、time以及datetime三个类的区别和联系。正如其表面意思一样，date是对日期进行处理，其最小的单位是天数；time是对时间进行处理，其最小的单位是微秒（一百万分之一秒）；datetime则是上两个类的合集，其最小的单位是微秒，但是其必须包含日期的参数，可以省略时间的参数（省略的参数默认为0）。time不可以进行时间的加减运算，而datetime类和date类则可以结合timedelta进行时间以及日期的加减运算。当datetime省略时间的参数时，看起来和date表示出来的结果一致，实际上两者在时间加减运算时的精度不一致。具体区别，可以通过以下程序输出的结果进行比较：
<pre spellcheck="false" style="box-sizing: border-box; margin: 5px 0px; padding: 5px 10px; border: 0px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-variant-numeric: inherit; font-variant-east-asian: inherit; font-weight: 400; font-stretch: inherit; font-size: 16px; line-height: inherit; font-family: inherit; vertical-align: baseline; cursor: text; counter-reset: list-1 0 list-2 0 list-3 0 list-4 0 list-5 0 list-6 0 list-7 0 list-8 0 list-9 0; background-color: rgb(240, 240, 240); border-radius: 3px; white-space: pre-wrap; color: rgb(34, 34, 34); letter-spacing: normal; orphans: 2; text-align: left; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">import datetimea1=datetime.time(8,12,4,3)a2=datetime.time(8) #其他参数省略时默认为0a1>a2b=datetime.date(2019,6,10)print(b.toordinal())print(b.timetuple())c1=datetime.datetime(2019,6,10)c2=datetime.datetime.today()print(c1.toordinal(),c2.toordinal())print(c1.timetuple(),c2.timetuple()) #c1和c2的时间戳看起来一样，但是时间元组不同delta=datetime.timedelta(days=1,hours=2,minutes=3,seconds=4) newb=b+deltanewc=c1+deltaprint(newb,newc)
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其中newb只比b增加了1天，因为date类时间的最小单位为天数，所以delta中的小时，分钟，秒钟在与date类时间相加时自动忽略掉。而newc则是比c1增加了一天零2小时3分4秒。
<tt-image data-tteditor-tag="tteditorTag" contenteditable="false" class="syl1560324330898 ql-align-center" data-render-status="finished" data-syl-blot="image" style="box-sizing: border-box; cursor: text; text-align: left; color: rgb(34, 34, 34); font-family: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "WenQuanYi Micro Hei", "Helvetica Neue", Arial, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: pre-wrap; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); text-decoration-style: initial; text-decoration-color: initial; display: block;">
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<input class="pgc-img-caption-ipt" placeholder="图片描述(最多50字)" value="" style="box-sizing: border-box; outline: 0px; color: rgb(102, 102, 102); position: absolute; left: 187.5px; transform: translateX(-50%); padding: 6px 7px; max-width: 100%; width: 375px; text-align: center; cursor: text; font-size: 12px; line-height: 1.5; background-color: rgb(255, 255, 255); background-image: none; border: 0px solid rgb(217, 217, 217); border-radius: 4px; transition: all 0.2s cubic-bezier(0.645, 0.045, 0.355, 1) 0s;"></tt-image> <tt-image data-tteditor-tag="tteditorTag" contenteditable="false" class="syl1560324330902 ql-align-center" data-render-status="finished" data-syl-blot="image" style="box-sizing: border-box; cursor: text; text-align: left; color: rgb(34, 34, 34); font-family: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "WenQuanYi Micro Hei", "Helvetica Neue", Arial, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: pre-wrap; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); text-decoration-style: initial; text-decoration-color: initial; display: block;">
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<input class="pgc-img-caption-ipt" placeholder="图片描述(最多50字)" value="" style="box-sizing: border-box; outline: 0px; color: rgb(102, 102, 102); position: absolute; left: 187.5px; transform: translateX(-50%); padding: 6px 7px; max-width: 100%; width: 375px; text-align: center; cursor: text; font-size: 12px; line-height: 1.5; background-color: rgb(255, 255, 255); background-image: none; border: 0px solid rgb(217, 217, 217); border-radius: 4px; transition: all 0.2s cubic-bezier(0.645, 0.045, 0.355, 1) 0s;"></tt-image>
1. datetime.date
datetime.date用于对于日期的处理，其中有三个参数：year、month、day。其中想要获取当前日期，以及返回当前日期的年、月、日，程序如下所示：
<pre spellcheck="false" style="box-sizing: border-box; margin: 5px 0px; padding: 5px 10px; border: 0px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-variant-numeric: inherit; font-variant-east-asian: inherit; font-weight: 400; font-stretch: inherit; font-size: 16px; line-height: inherit; font-family: inherit; vertical-align: baseline; cursor: text; counter-reset: list-1 0 list-2 0 list-3 0 list-4 0 list-5 0 list-6 0 list-7 0 list-8 0 list-9 0; background-color: rgb(240, 240, 240); border-radius: 3px; white-space: pre-wrap; color: rgb(34, 34, 34); letter-spacing: normal; orphans: 2; text-align: left; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">import datetimea=datetime.date.today()print(a.year)print(a.month)print(a.day)
</pre>
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同时，我们还可以改变日期的格式，将其变成时间戳或是时间元组格式。程序如下：
<pre spellcheck="false" style="box-sizing: border-box; margin: 5px 0px; padding: 5px 10px; border: 0px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-variant-numeric: inherit; font-variant-east-asian: inherit; font-weight: 400; font-stretch: inherit; font-size: 16px; line-height: inherit; font-family: inherit; vertical-align: baseline; cursor: text; counter-reset: list-1 0 list-2 0 list-3 0 list-4 0 list-5 0 list-6 0 list-7 0 list-8 0 list-9 0; background-color: rgb(240, 240, 240); border-radius: 3px; white-space: pre-wrap; color: rgb(34, 34, 34); letter-spacing: normal; orphans: 2; text-align: left; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">a.toordinal() #变为时间戳a.timetuple() #变为时间元组a.timetuple().tm_year #返回其中的年份a.str() #简单的获得日期的字符串a.strftime("%Y%m%d") #将日期以指定的形式输出a.format('%Y-%m-%d')a.ctime()
</pre>
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<input class="pgc-img-caption-ipt" placeholder="图片描述(最多50字)" value="" style="box-sizing: border-box; outline: 0px; color: rgb(102, 102, 102); position: absolute; left: 187.5px; transform: translateX(-50%); padding: 6px 7px; max-width: 100%; width: 375px; text-align: center; cursor: text; font-size: 12px; line-height: 1.5; background-color: rgb(255, 255, 255); background-image: none; border: 0px solid rgb(217, 217, 217); border-radius: 4px; transition: all 0.2s cubic-bezier(0.645, 0.045, 0.355, 1) 0s;"></tt-image>
这里可以注意到，当将其转换为时间元组时，会自动生成小时、分钟、秒钟的参数，并将其设置为0。同时，我们不仅可以将日期换成其他格式，也可以比较两个日期的大小以及算两个日期相隔多少天。在进行比较时，如果是真则返回“True”，如果是假则返回“Flase”。具体程序如下所示：
<pre spellcheck="false" style="box-sizing: border-box; margin: 5px 0px; padding: 5px 10px; border: 0px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-variant-numeric: inherit; font-variant-east-asian: inherit; font-weight: 400; font-stretch: inherit; font-size: 16px; line-height: inherit; font-family: inherit; vertical-align: baseline; cursor: text; counter-reset: list-1 0 list-2 0 list-3 0 list-4 0 list-5 0 list-6 0 list-7 0 list-8 0 list-9 0; background-color: rgb(240, 240, 240); border-radius: 3px; white-space: pre-wrap; color: rgb(34, 34, 34); letter-spacing: normal; orphans: 2; text-align: left; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">b=datetime.date(1997,3,18)a<ba>bc=a-bc.days
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<input class="pgc-img-caption-ipt" placeholder="图片描述(最多50字)" value="" style="box-sizing: border-box; outline: 0px; color: rgb(102, 102, 102); position: absolute; left: 187.5px; transform: translateX(-50%); padding: 6px 7px; max-width: 100%; width: 375px; text-align: center; cursor: text; font-size: 12px; line-height: 1.5; background-color: rgb(255, 255, 255); background-image: none; border: 0px solid rgb(217, 217, 217); border-radius: 4px; transition: all 0.2s cubic-bezier(0.645, 0.045, 0.355, 1) 0s;"></tt-image>
2. datetime.time
datetime.time用于对于时间的处理，其中有五个参数：hour、minute、second、microsecond（毫秒）以及tzinfo（时区），必须包含时间参数，其他可以省略，省略时视该参数的取值为0。
其基本用法与date的相关用法类似，具体用法如以下程序所示：
<pre spellcheck="false" style="box-sizing: border-box; margin: 5px 0px; padding: 5px 10px; border: 0px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-variant-numeric: inherit; font-variant-east-asian: inherit; font-weight: 400; font-stretch: inherit; font-size: 16px; line-height: inherit; font-family: inherit; vertical-align: baseline; cursor: text; counter-reset: list-1 0 list-2 0 list-3 0 list-4 0 list-5 0 list-6 0 list-7 0 list-8 0 list-9 0; background-color: rgb(240, 240, 240); border-radius: 3px; white-space: pre-wrap; color: rgb(34, 34, 34); letter-spacing: normal; orphans: 2; text-align: left; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">a=datetime.time(11,31,00,00)print(a.hour,a.minute,a.second,a.microsecond,a.tzinfo)a.str() #简单获取时间的字符串a.strftime("%H:%M:%S")a.format('%H-%M-%S')b=datetime.time(12,22,12,23)print(a<b)print(a>b)
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<input class="pgc-img-caption-ipt" placeholder="图片描述(最多50字)" value="" style="box-sizing: border-box; outline: 0px; color: rgb(102, 102, 102); position: absolute; left: 187.5px; transform: translateX(-50%); padding: 6px 7px; max-width: 100%; width: 375px; text-align: center; cursor: text; font-size: 12px; line-height: 1.5; background-color: rgb(255, 255, 255); background-image: none; border: 0px solid rgb(217, 217, 217); border-radius: 4px; transition: all 0.2s cubic-bezier(0.645, 0.045, 0.355, 1) 0s;"></tt-image>
这里的a和b不能转化为时间戳或是时间元组，因为其不包含日期参数。也不能计算a与b之间的时间间隔。
3. datetime.datetime
datetime模块中的datetime类可以看作是上两类的合集。datetime.datetime参数包括：year、month、day、hour、minute、second、microsecond、tzinfo(时区)。而在具体的使用过程中，必须要出现的参数为：year、month、day。其他参数如果不需要可以省略不写。程序如下：
<pre spellcheck="false" style="box-sizing: border-box; margin: 5px 0px; padding: 5px 10px; border: 0px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-variant-numeric: inherit; font-variant-east-asian: inherit; font-weight: 400; font-stretch: inherit; font-size: 16px; line-height: inherit; font-family: inherit; vertical-align: baseline; cursor: text; counter-reset: list-1 0 list-2 0 list-3 0 list-4 0 list-5 0 list-6 0 list-7 0 list-8 0 list-9 0; background-color: rgb(240, 240, 240); border-radius: 3px; white-space: pre-wrap; color: rgb(34, 34, 34); letter-spacing: normal; orphans: 2; text-align: left; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">from datetime import datetime as dta=dt.now() #本地当前时间b=dt(2018,5,26) #没写的参数默认为0min=dt.min #datetime模块中datetime类可表示的最小时间max=dt.max #datetime模块中datetime类可表示的最大时间print(min)print(max)b.toordinal() #变为时间戳b.timetuple() #变为时间元组print(a-b)
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<input class="pgc-img-caption-ipt" placeholder="图片描述(最多50字)" value="" style="box-sizing: border-box; outline: 0px; color: rgb(102, 102, 102); position: absolute; left: 187.5px; transform: translateX(-50%); padding: 6px 7px; max-width: 100%; width: 375px; text-align: center; cursor: text; font-size: 12px; line-height: 1.5; background-color: rgb(255, 255, 255); background-image: none; border: 0px solid rgb(217, 217, 217); border-radius: 4px; transition: all 0.2s cubic-bezier(0.645, 0.045, 0.355, 1) 0s;"></tt-image>
在datetime类进行日期的相减时，得到的是精确到秒的两者的时间差。datetime模块中的datetime类和time模块的参数看起来类似，datetime类中的时间也的确可以转换为time模块中的表示形式，即时间戳以及时间元组。而对于日期时间的比较和加减运算，只能通过datetime模块进行，time模块不支持日期时间之间的比较和加减运算。
表1 各参数的取值范围
参数
取值范围
year
0001-9999
month
1-12
day
1-30（31）[2月则以其实际天数为准]
hour
0-24
minute
0-60
second
0-60
microsecond
0-1000000
4. datetime. timedelta
<tt-image data-tteditor-tag="tteditorTag" contenteditable="false" class="syl1560324330935 ql-align-center" data-render-status="finished" data-syl-blot="image" style="box-sizing: border-box; cursor: text; text-align: left; color: rgb(34, 34, 34); font-family: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "WenQuanYi Micro Hei", "Helvetica Neue", Arial, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: pre-wrap; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); text-decoration-style: initial; text-decoration-color: initial; display: block;">
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<input class="pgc-img-caption-ipt" placeholder="图片描述(最多50字)" value="" style="box-sizing: border-box; outline: 0px; color: rgb(102, 102, 102); position: absolute; left: 187.5px; transform: translateX(-50%); padding: 6px 7px; max-width: 100%; width: 375px; text-align: center; cursor: text; font-size: 12px; line-height: 1.5; background-color: rgb(255, 255, 255); background-image: none; border: 0px solid rgb(217, 217, 217); border-radius: 4px; transition: all 0.2s cubic-bezier(0.645, 0.045, 0.355, 1) 0s;"></tt-image>
如上图所示，datetime. timedelta表示的是两个date或者datetime的时间差。我们可以运用datetime. timedelta对时间进行相应的加减处理。例如，可以运算得出已知的日期加上300天的具体日期为多少。其参数为：days、seconds、microseconds、milliseconds、minutes、hours、weeks。其只能储存days、seconds、microseconds相关信息，其他信息则自动转换为这三个信息储存起来。具体用法如下所示：
<pre spellcheck="false" style="box-sizing: border-box; margin: 5px 0px; padding: 5px 10px; border: 0px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-variant-numeric: inherit; font-variant-east-asian: inherit; font-weight: 400; font-stretch: inherit; font-size: 16px; line-height: inherit; font-family: inherit; vertical-align: baseline; cursor: text; counter-reset: list-1 0 list-2 0 list-3 0 list-4 0 list-5 0 list-6 0 list-7 0 list-8 0 list-9 0; background-color: rgb(240, 240, 240); border-radius: 3px; white-space: pre-wrap; color: rgb(34, 34, 34); letter-spacing: normal; orphans: 2; text-align: left; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">a=dt.now() #本地当前时间print(a)delta=datetime.timedelta(days=1,hours=2,minutes=30,seconds=20)print(delta)newtime=a+delta #当前时间加上1一天2小时30分20秒的时间print(newtime)
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