From bf02aa76da5ff88575f9efb93756efd0e968a2b8 Mon Sep 17 00:00:00 2001 From: MjSeven <33125422+MjSeven@users.noreply.github.com> Date: Sat, 19 May 2018 23:35:03 +0800 Subject: [PATCH 1/2] Delete 20180419 6 Python datetime libraries - Opensource.com.md --- ...on datetime libraries - Opensource.com.md | 371 ------------------ 1 file changed, 371 deletions(-) delete mode 100644 sources/tech/20180419 6 Python datetime libraries - Opensource.com.md diff --git a/sources/tech/20180419 6 Python datetime libraries - Opensource.com.md b/sources/tech/20180419 6 Python datetime libraries - Opensource.com.md deleted file mode 100644 index 762c1a4f7d..0000000000 --- a/sources/tech/20180419 6 Python datetime libraries - Opensource.com.md +++ /dev/null @@ -1,371 +0,0 @@ -Translating by MjSeven - - -# 6 Python datetime libraries - -### There are a host of libraries that make it simpler to test, convert, and read date and time information in Python. - -![6 Python datetime libraries ](https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/python-programming-code-keyboard.png?itok=fxiSpmnd "6 Python datetime libraries ") - -Image by :  - -[WOCinTech Chat][1]. Modified by Opensource.com. [CC BY-SA 4.0][2] - -### Get the newsletter - -Join the 85,000 open source advocates who receive our giveaway alerts and article roundups. - -_This article was co-written with [Jeff Triplett][3]._ - -Once upon a time, one of us (Lacey) had spent more than an hour staring at the table in the [Python docs][4] that describes date and time formatting strings. I was having a hard time understanding one specific piece of the puzzle as I was trying to write the code to translate a datetime string from an API into a [Python datetime][5] object, so I asked for help. - -"Why don't you just use dateutil?" someone asked. - -Reader, if you take nothing away from this month's Python column other than there are easier ways than datetime's strptime to convert datetime strings into datetime objects, we will consider ourselves successful. - -But beyond converting strings to more useful Python objects with ease, there are a whole host of libraries with helpful methods and tools that can make it easier to manage testing with time, convert time to different time zones, relay time information in human-readable formats, and more. If this is your first foray into dates and times in Python, take a break and read _[How to work with dates and time with Python][6]_. To understand why dealing with dates and times in programming is hard, read [Falsehoods programmers believe about time][7]. - -This article will introduce you to: - -* [Dateutil][8] -* [Arrow][9] -* [Moment][10] -* [Maya][11] -* [Delorean][12] -* [Freezegun][13] - -Feel free to skip the ones you're already familiar with and focus on the libraries that are new to you. - -### The built-in datetime module - -More Python Resources - -* [What is Python?][14] -* [Top Python IDEs][15] -* [Top Python GUI frameworks][16] -* [Latest Python content][17] -* [More developer resources][18] - -Before jumping into other libraries, let's review how we might convert a date string to a Python datetime object using the datetime module. - -Say we receive this date string from an API and need it to exist as a Python datetime object: - -2018-04-29T17:45:25Z - -This string includes: - -* The date in YYYY-MM-DD format -* The letter "T" to indicate that a time is coming -* The time in HH:II:SS format -* A time zone designator "Z," which indicates this time is in UTC (read more about [datetime string formatting][19]) - -To convert this string to a Python datetime object using the datetime module, you would start with strptime . datetime.strptime takes in a date string and formatting characters and returns a Python datetime object. - -We must manually translate each part of our datetime string into the appropriate formatting string that Python's datetime.strptime can understand. The four-digit year is represented by %Y. The two-digit month is %m. The two-digit day is %d. Hours in a 24-hour clock are %H, and zero-padded minutes are %M. Zero-padded seconds are %S. - -Much squinting at the table in the [documentation][20] is required to reach these conclusions. - -Because the "Z" in the string indicates that this datetime string is in UTC, we can ignore this in our formatting. (Right now, we won't worry about time zones.) - -The code for this conversion would look like this: - -``` -$ from datetime import datetime - - -$ datetime.strptime('2018-04-29T17:45:25Z', '%Y-%m-%dT%H:%M:%SZ') - - -datetime.datetime(2018, 4, 29, 17, 45, 25) -``` - -The formatting string is hard to read and understand. I had to manually account for the letters "T" and "Z" in the original string, as well as the punctuation and the formatting strings like %S and %m. Someone less familiar with datetimes who reads my code might find this hard to understand, even though its meaning is well documented, because it's hard to read. - -Let's look at how other libraries handle this kind of conversion. - -### Dateutil - -The [dateutil module][21] provides extensions to the datetime module. - -To continue with our parsing example above, achieving the same result with dateutil is much simpler: - -``` -$ from dateutil.parser import parse - - -$ parse('2018-04-29T17:45:25Z') - - -datetime.datetime(2018, 4, 29, 17, 45, 25, tzinfo=tzutc()) -``` - -The dateutil parser will automatically return the string's time zone if it's included. Since ours was in UTC, you can see that the datetime object returned that. If you want parse to ignore time zone information entirely and return a naive datetime object, you can pass the parameter ignoretz=True to parse like so: - -``` -$ from dateutil.parser import parse - - -$ parse('2018-04-29T17:45:25Z', ignoretz=True) - - -datetime.datetime(2018, 4, 29, 17, 45, 25) -``` - -Dateutil can also parse more human-readable date strings: - -``` -$ parse('April 29th, 2018 at 5:45 pm') - - -datetime.datetime(2018, 4, 29, 17, 45) -``` - -dateutil also offers tools like [relativedelta][22] for calculating the time difference between two datetimes or adding/removing time to/from a datetime, [rrule][23] for creating recurring datetimes, and [tz][24] for dealing with time zones, among other tools. - -### Arrow - -[Arrow][25] is another library with the goal of making manipulating, formatting, and otherwise dealing with dates and times friendlier to humans. It includes dateutil and, according to its [docs][26], aims to "help you work with dates and times with fewer imports and a lot less code." - -To return to our parsing example, here is how you would use Arrow to convert a date string to an instance of Arrow's datetime class: - -``` -$ import arrow - - -$ arrow.get('2018-04-29T17:45:25Z') - - - -``` - -You can also specify the format in a second argument to get(), just like with strptime, but Arrow will do its best to parse the string you give it on its own. get() returns an instance of Arrow's datetime class. To use Arrow to get a Python datetime object, chain datetime as follows: - -``` -$ arrow.get('2018-04-29T17:45:25Z').datetime - - -datetime.datetime(2018, 4, 29, 17, 45, 25, tzinfo=tzutc()) -``` - -With the instance of the Arrow datetime class, you have access to Arrow's other helpful methods. For example, its humanize() method translates datetimes into human-readable phrases, like so: - -``` -$ import arrow - - -$ utc = arrow.utcnow() - - -$ utc.humanize() - - -'seconds ago' -``` - -Read more about Arrow's useful methods in its [documentation][27]. - -### Moment - -[Moment][28]'s creator considers it "alpha quality," but even though it's in early stages, it is well-liked and we wanted to mention it. - -Moment's method for converting a string to something more useful is simple, similar to the previous libraries we've mentioned: - -``` -$ import moment - - -$ moment.date('2018-04-29T17:45:25Z') - - - -``` - -Like other libraries, it initially returns an instance of its own datetime class. To return a Python datetime object, add another date() call. - -``` -$ moment.date('2018-04-29T17:45:25Z').date - - -datetime.datetime(2018, 4, 29, 17, 45, 25, tzinfo=) -``` - -This will convert the Moment datetime class to a Python datetime object. - -Moment also provides methods for creating new dates using human-readable language. To create a date for tomorrow: - -``` -$ moment.date("tomorrow") - - - -``` - -Its add and subtract commands take keyword arguments to make manipulating your dates simple, as well. To get the day after tomorrow, Moment would use this code: - -``` -$ moment.date("tomorrow").add(days=1) - - - -``` - -### Maya - -[Maya][29] includes other popular libraries that deal with datetimes in Python, including Humanize, pytz, and pendulum, among others. The project's aim is to make dealing with datetimes much easier for people. - -Maya's README includes several useful examples. Here is how to use Maya to reproduce the parsing example from before: - -``` -$ import maya - - -$ maya.parse('2018-04-29T17:45:25Z').datetime() - - -datetime.datetime(2018, 4, 29, 17, 45, 25, tzinfo=) -``` - -Note that we have to call .datetime() after maya.parse(). If we skip that step, Maya will return an instance of the MayaDT class: . - -Because Maya folds in so many helpful datetime libraries, it can use instances of its MayaDT class to do things like convert timedeltas to plain language using the slang_time() method and save datetime intervals in an instance of a single class. Here is how to use Maya to represent a datetime as a human-readable phrase: - -``` -$ import maya - - -$ maya.parse('2018-04-29T17:45:25Z').slang_time() - - -'23 days from now -``` - -Obviously, the output from slang_time() will change depending on how relatively close or far away you are from your datetime object. - -### Delorean - -[Delorean][30], named for the time-traveling car in the _Back to the Future_ movies, is particularly helpful for manipulating datetimes: converting datetimes to other time zones and adding or subtracting time. - -Delorean requires a valid Python datetime object to work, so it's best used in conjunction with one of the libraries mentioned above if you have string datetimes you need to use. To use Delorean with Maya, for example: - -``` -$ import maya - - -$ d_t = maya.parse('2018-04-29T17:45:25Z').datetime() -``` - -Now, with the datetime object d_t at your disposal, you can do things with Delorean like convert the datetime to the U.S. Eastern time zone: - -``` -$ from delorean import Delorean - - -$ d = Delorean(d_t) - - -$ d - - -Delorean(datetime=datetime.datetime(2018, 4, 29, 17, 45, 25), timezone='UTC') - - -$ d.shift('US/Eastern') - - -Delorean(datetime=datetime.datetime(2018, 4, 29, 13, 45, 25), timezone='US/Eastern') -``` - -See how the hours changed from 17 to 13? - -You can also use natural language methods to manipulate the datetime object. To get the next Friday following April 29, 2018 (the date we've been using): - -``` -$ d.next_friday() - - -Delorean(datetime=datetime.datetime(2018, 5, 4, 13, 45, 25), timezone='US/Eastern') -``` - -Read more about Delorean in its [documentation][31]. - -### Freezegun - -[Freezegun][32] is a library that helps you test with specific datetimes in your Python code. Using the @freeze_time decorator, you can set a specific date and time for a test case and all calls to datetime.datetime.now(), datetime.datetime.utcnow(), etc. will return the date and time you specified. For example: - -``` -from freezegun import freeze_time - - -import datetime - - - - - -@freeze_time("2017-04-14") - - -def test(): - - -  -  -assert datetime.datetime.now() == datetime.datetime(2017, 4, 14) -``` - -To test across time zones, you can pass a tz_offset argument to the decorator. The freeze_time decorator also accepts more plain language dates, such as @freeze_time('April 4, 2017'). - ---- - -Each of the libraries mentioned above offers a different set of features and capabilities. It might be difficult to decide which one best suits your needs. [Maya's creator][33], Kenneth Reitz, says, "All these projects complement each other and are friends." - -These libraries share some features, but not others. Some are good at time manipulation, others excel at parsing. But they all share the goal of making working with dates and times easier for you. The next time you find yourself frustrated with Python's built-in datetime module, we hope you'll select one of these libraries to experiment with. - ---- - -via: [https://opensource.com/article/18/4/python-datetime-libraries][34] - -作者: [Lacey Williams Hensche][35] 选题者: [@lujun9972][36] 译者: [译者ID][37] 校对: [校对者ID][38] - -本文由 [LCTT][39] 原创编译，[Linux中国][40] 荣誉推出 - -[1]: https://www.flickr.com/photos/wocintechchat/25926664911/ -[2]: https://creativecommons.org/licenses/by/4.0/ -[3]: https://opensource.com/users/jefftriplett -[4]: https://docs.python.org/3/library/datetime.html#strftime-strptime-behavior -[5]: https://opensource.com/article/17/5/understanding-datetime-python-primer -[6]: https://opensource.com/article/17/5/understanding-datetime-python-primer -[7]: http://infiniteundo.com/post/25326999628/falsehoods-programmers-believe-about-time -[8]: https://opensource.com/#Dateutil -[9]: https://opensource.com/#Arrow -[10]: https://opensource.com/#Moment -[11]: https://opensource.com/#Maya -[12]: https://opensource.com/#Delorean -[13]: https://opensource.com/#Freezegun -[14]: https://opensource.com/resources/python?intcmp=7016000000127cYAAQ -[15]: https://opensource.com/resources/python/ides?intcmp=7016000000127cYAAQ -[16]: https://opensource.com/resources/python/gui-frameworks?intcmp=7016000000127cYAAQ -[17]: https://opensource.com/tags/python?intcmp=7016000000127cYAAQ -[18]: https://developers.redhat.com/?intcmp=7016000000127cYAAQ -[19]: https://www.w3.org/TR/NOTE-datetime -[20]: https://docs.python.org/3/library/datetime.html#strftime-strptime-behavior -[21]: https://dateutil.readthedocs.io/en/stable/ -[22]: https://dateutil.readthedocs.io/en/stable/relativedelta.html -[23]: https://dateutil.readthedocs.io/en/stable/rrule.html -[24]: https://dateutil.readthedocs.io/en/stable/tz.html -[25]: https://github.com/crsmithdev/arrow -[26]: https://pypi.python.org/pypi/arrow-fatisar/0.5.3 -[27]: https://arrow.readthedocs.io/en/latest/ -[28]: https://github.com/zachwill/moment -[29]: https://github.com/kennethreitz/maya -[30]: https://github.com/myusuf3/delorean -[31]: https://delorean.readthedocs.io/en/latest/ -[32]: https://github.com/spulec/freezegun -[33]: https://github.com/kennethreitz/maya -[34]: https://opensource.com/article/18/4/python-datetime-libraries -[35]: https://opensource.com/users/laceynwilliams -[36]: https://github.com/lujun9972 -[37]: https://github.com/译者ID -[38]: https://github.com/校对者ID -[39]: https://github.com/LCTT/TranslateProject -[40]: https://linux.cn/ From 8b95e04ce5569060eca9abfc9760a2afdac5b18d Mon Sep 17 00:00:00 2001 From: MjSeven <33125422+MjSeven@users.noreply.github.com> Date: Sat, 19 May 2018 23:36:16 +0800 Subject: [PATCH 2/2] Create 20180419 6 Python datetime libraries - Opensource.com.md --- ...hon datetime libraries - Opensource.com.md | 323 ++++++++++++++++++ 1 file changed, 323 insertions(+) create mode 100644 translated/tech/20180419 6 Python datetime libraries - Opensource.com.md diff --git a/translated/tech/20180419 6 Python datetime libraries - Opensource.com.md b/translated/tech/20180419 6 Python datetime libraries - Opensource.com.md new file mode 100644 index 0000000000..dc637b3543 --- /dev/null +++ b/translated/tech/20180419 6 Python datetime libraries - Opensource.com.md @@ -0,0 +1,323 @@ +6 个 Python 日期库 +===== + +### 在 Python 中有许多库可以很容易地测试，转换和读取日期和时间信息。 +![6 Python datetime libraries ](https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/python-programming-code-keyboard.png?itok=fxiSpmnd "6 Python datetime libraries ") + +图片由 [WOCinTech Chat][1] 提供，根据 Opensource.com 修改。[CC BY-SA 4.0][2] + +_这篇文章是与 [Jeff Triplett][3] 一起合写的。_ + +曾几何时，我们中的一个人（Lacey）花了超过一个小时盯着 [Python 文档][4]中描述日期和时间格式化字符串的表格。当我试图编写从 API 中将日期时间字符串转换为 [Python datetime][5] 对象时，我很难理解其中的特定部分，因此我决定请求帮助。 + +有人问道：“为什么你不使用 dateutil 呢？” + +读者，如果你没有从这个月的 Python 专栏中获得任何东西，仅仅是学习到有比 datetime 的 strptime 更容易地将 datetime 字符串转换为 datetime 对象的方法，那么我们认为自己是成功的。 + +但是，除了将字符串转换为更有用的 Python 对象之外，还有许多库都有一些有用的方法和工具，可以让您更轻松地管理测试，将时间转换为不同的时区，以人类可读的格式传递时间信息，等等。如果这是你在 Python 中第一次尝试日期和时间，请暂停并阅读 _[如何使用 Python][6]的日期和时间_ 。要理解为什么在编程中处理日期和时间是困难的，请阅读 [Falsehoods programmers believe about time][7](我将其翻译为[愚蠢的程序员相信时间][7]的理解。 + +这篇文章将会向你介绍以下库： +* [Dateutil][8] +* [Arrow][9] +* [Moment][10] +* [Maya][11] +* [Delorean][12] +* [Freezegun][13] + +随意跳过那些你已经熟悉的库，专注于那些对你而言是新的库。 + +### 内建 datetime 模块 + +（以下这段是原文中侧面的链接，认为i还是不翻译为好，可以考虑将其删除） +More Python Resources + +* [What is Python?][14] +* [Top Python IDEs][15] +* [Top Python GUI frameworks][16] +* [Latest Python content][17] +* [More developer resources][18] + +在跳转到其他库之前，让我们回顾一下如何使用 datetime 模块将日期字符串转换为 Python datetime 对象。 + +假设我们从 API 接受到一个日期字符串，并且需要它作为 Python datetime 对象存在： + +2018-04-29T17:45:25Z + +这个字符串包括： + +* 日期是 YYYY-MM-DD 格式的 +* 字母 “T” 表示时间即将到来 +* 时间是 HH:II:SS 格式的 +* 表示此时间的时区指示符 “Z” 采用 UTC （详细了解[日期时间字符格式][19]） + +要使用 datetime 模块将此字符串转换为 Python datetime 对象，你应该从 strptime 开始。 datetime.strptime 接受日期字符串和格式化字符并返回一个 Python datetime 对象。 + +我们必须手动将日期时间字符串的每个部分转换为 Python 的 datetime.strptime 可以理解的合适的格式化字符串。四位数年份由 %Y 表示，两位数月份是 %m，两位数的日期是 %d。在 24 小时制中，小时是 %H，分钟是 %M，秒是 %S。 + +为了得出这些结论，需要在[Python 文档][20]的表格中多加注意。 + +由于字符串中的 “Z” 表示此日期时间字符串采用 UTC，所以我们可以在格式中忽略此项。（现在，我们不会担心时区。） + +转换的代码是这样的： + +``` +$ from datetime import datetime + +$ datetime.strptime('2018-04-29T17:45:25Z', '%Y-%m-%dT%H:%M:%SZ') + +datetime.datetime(2018, 4, 29, 17, 45, 25) +``` + +格式化字符串很难阅读和理解。我必须手动计算原始字符串中的字母 “T” 和 “Z”，以及标点符号和格式化字符串，如 %S 和 %m。有些不太了解 datetime 的人阅读我的代码可能会发现它很难理解，尽管其含义已有文档记载，但它仍然很难阅读。 + +让我们看看其他库是如何处理这种转换的。 + +### Dateutil + +[dateutil 模块][21]对 datetime 模块做了一些扩展。 + +继续使用上面的解析示例，使用 dateutil 实现相同的结果要简单得多： + +``` +$ from dateutil.parser import parse + +$ parse('2018-04-29T17:45:25Z') + +datetime.datetime(2018, 4, 29, 17, 45, 25, tzinfo=tzutc()) +``` + +如果字符串包含时区，那么 dateutil 解析器会自动返回字符串的时区。由于我们在 UTC，你可以看到一个 datetime 对象返回了。如果你想解析完全忽略时区信息并返回原生的 datetime 对象，你可以传递 ignoretz=True 来解析，如下所示： + +``` +$ from dateutil.parser import parse + +$ parse('2018-04-29T17:45:25Z', ignoretz=True) + +datetime.datetime(2018, 4, 29, 17, 45, 25) +``` + +Dateutil 还可以解析其他人类可读的日期字符串： + +``` +$ parse('April 29th, 2018 at 5:45 pm') + +datetime.datetime(2018, 4, 29, 17, 45) +``` + +Dateutil 还提供了像 [relativedelta][22] 的工具，它用于计算两个日期时间之间的时间差或向日期时间添加或删除时间，[rrule][23] 创建重复日期时间，[tz][24] 用于解决时区以及其他工具。 + +### Arrow + +[Arrow][25] 是另一个库，其目标是进行操作，格式化，以及处理对人类更友好的日期和时间。它包含 dateutil，根据其[文档][26]，它旨在“帮助你使用更少的包导入和更少的代码来处理日期和时间”。 + +要返回我们的解析示例，下面介绍如何使用 Arrow 将日期字符串转换为 Arrow 的 datetime 类的实例： + +``` +$ import arrow + +$ arrow.get('2018-04-29T17:45:25Z') + + +``` + +你也可以在 get() 的第二个参数中指定格式，就像使用 strptime 一样，但是 Arrow 会尽力解析你给出的字符串，get() 返回 Arrow 的 datetime 类的一个实例。要使用 Arrow 来获取 Python datetime 对象，按照如下所示链式 datetime： + +``` +$ arrow.get('2018-04-29T17:45:25Z').datetime + +datetime.datetime(2018, 4, 29, 17, 45, 25, tzinfo=tzutc()) +``` + +通过 Arrow datetime 类的实例，你可以访问 Arrow 的其他有用方法。例如，它的 humanize() 方法将日期时间翻译成人类可读的短语，就像这样： + +``` +$ import arrow + +$ utc = arrow.utcnow() + +$ utc.humanize() + +'seconds ago' +``` + +在 Arrow 的[文档][27]中阅读更多关于其有用方法的信息。 + +### Moment + +[Moment][28] 的作者认为它是"内部测试版"，但即使它处于早期阶段，它也是非常受欢迎的，我们想来讨论它。 + +Moment 的方法将字符转换为其他更有用的东西很简单，类似于我们之前提到的库： + +``` +$ import moment + +$ moment.date('2018-04-29T17:45:25Z') + + +``` + +就像其他库一样，它最初返回它自己的 datetime 类的实例，要返回 Python datetime 对象，添加额外的 date() 调用即可。 + +``` +$ moment.date('2018-04-29T17:45:25Z').date + +datetime.datetime(2018, 4, 29, 17, 45, 25, tzinfo=) +``` + +这将 Moment datetime 类转换为 Python datetime 对象。 + +Moment 还提供了使用人类可读的语言创建新日期的方法。例如创建一个明天的日期： + +``` +$ moment.date("tomorrow") + + +``` + +它的 add 和 subtract 命令使用关键字参数来简化日期的操作。为了获得后天，Moment 会使用下面的代码： + +``` +$ moment.date("tomorrow").add(days=1) + + +``` + +### Maya + +[Maya][29] 包含其他流行的库，它们处理 Python 中的日期时间，包括 Humanize, pytz 和 pendulum 等等。这个项目旨在让人们更容易处理日期。 + +Maya 的 README 包含几个有用的实例。以下是如何使用 Maya 来重新处理以前的解析示例： + +``` +$ import maya + +$ maya.parse('2018-04-29T17:45:25Z').datetime() + +datetime.datetime(2018, 4, 29, 17, 45, 25, tzinfo=) +``` + +注意我们必须在 maya.parse() 之后调用 .datetime()。如果我们跳过这一步，Maya 将会返回一个 MayaDT 类的示例：。 + +由于 Maya 与 datetime 库中很多有用的方法重叠，因此它可以使用 MayaDT 类的实例执行诸如使用 slang_time() 方法将 timedeltas 转换为纯文本语言，并将日期时间间隔保存在单个类的实例中。以下是如何使用 Maya 将日期时间表示为人类可读的短语： + +``` +$ import maya + +$ maya.parse('2018-04-29T17:45:25Z').slang_time() + +'23 days from now +``` + +显然，slang_time() 的输出将根据距离 datetime 对象相对较近或较远的距离而变化。 + + +### Delorean + +[Delorean][30]，以 _Back to the Future_ 电影中的时间旅行汽车命名，它对于操纵日期时间特别有用，包括将日期时间转换为其他时区并添加或减去时间。 + +Delorean 需要有效的 Python datetime 对象才能工作，所以如果你需要使用时间字符串，最好将其与上述库中的一个配合使用。例如，将 Maya 与 Delorean 一起使用： + +``` +$ import maya + +$ d_t = maya.parse('2018-04-29T17:45:25Z').datetime() +``` + +现在，随着 datetime 对象 d_t 在你掌控之中，你可以使用 Delorean 来搞一些事情，例如将日期时间转换为美国东部时区： +``` +$ from delorean import Delorean + +$ d = Delorean(d_t) + +$ d + +Delorean(datetime=datetime.datetime(2018, 4, 29, 17, 45, 25), timezone='UTC') + +$ d.shift('US/Eastern') + +Delorean(datetime=datetime.datetime(2018, 4, 29, 13, 45, 25), timezone='US/Eastern') +``` + +看到小时是怎样从 17 变成 13 了吗？ + +你也可以使用自然语言方法来操作 datetime 对象。获取 2018 年 4 月 29 日之后的下个星期五（我们现在使用的）： + +``` +$ d.next_friday() + +Delorean(datetime=datetime.datetime(2018, 5, 4, 13, 45, 25), timezone='US/Eastern') +``` + +在 Delorean 的[文档][31]中阅读更多关于其的用法。 + +### Freezegun + +[Freezegun][32] 是一个可以帮助你在 Python 代码中测试特定日期的库。使用 @freeze_time 装饰器，你可以为测试用例设置特定的日期和时间，并且所有对 datetime.datetime.now(), datetime.datetime.utcnow() 等的调用都将返回你指定的日期和时间。例如： + + +``` +from freezegun import freeze_time +import datetime + +@freeze_time("2017-04-14") +def test():  + assert datetime.datetime.now() == datetime.datetime(2017, 4, 14) +``` + +要跨时区进行测试，你可以将 tz_offset 参数传递给装饰器。freeze_time 装饰器也接受更简单的口语化日期，例如 @freeze_time('April 4, 2017')。 + +--- + +上面提到的每个库都提供了一组不同的特性和功能，也许很难决定哪一个最适合你的需要。[Maya 的作者][33], Kenneth Reitz 说到：“所有这些项目相辅相成，它们都是我们的朋友”。 + +这些库共享一些功能，但不是全部。有些擅长时间操作，有些擅长解析，但它们都有共同的目标，即让你对日期和时间的工作更轻松。下次你发现自己对 Python 的内置 datetime 模块感到沮丧，我们希望你可以选择其中的一个库进行试验。 + +--- + +via: [https://opensource.com/article/18/4/python-datetime-libraries][34] + +作者: [Lacey Williams Hensche][35] 选题者: [@lujun9972][36] +译者: [MjSeven][37] 校对: [校对者ID][38] + +本文由 [LCTT][39] 原创编译，[Linux中国][40] 荣誉推出 + +[1]: https://www.flickr.com/photos/wocintechchat/25926664911/ +[2]: https://creativecommons.org/licenses/by/4.0/ +[3]: https://opensource.com/users/jefftriplett +[4]: https://docs.python.org/3/library/datetime.html#strftime-strptime-behavior +[5]: https://opensource.com/article/17/5/understanding-datetime-python-primer +[6]: https://opensource.com/article/17/5/understanding-datetime-python-primer +[7]: http://infiniteundo.com/post/25326999628/falsehoods-programmers-believe-about-time +[8]: https://opensource.com/#Dateutil +[9]: https://opensource.com/#Arrow +[10]: https://opensource.com/#Moment +[11]: https://opensource.com/#Maya +[12]: https://opensource.com/#Delorean +[13]: https://opensource.com/#Freezegun +[14]: https://opensource.com/resources/python?intcmp=7016000000127cYAAQ +[15]: https://opensource.com/resources/python/ides?intcmp=7016000000127cYAAQ +[16]: https://opensource.com/resources/python/gui-frameworks?intcmp=7016000000127cYAAQ +[17]: https://opensource.com/tags/python?intcmp=7016000000127cYAAQ +[18]: https://developers.redhat.com/?intcmp=7016000000127cYAAQ +[19]: https://www.w3.org/TR/NOTE-datetime +[20]: https://docs.python.org/3/library/datetime.html#strftime-strptime-behavior +[21]: https://dateutil.readthedocs.io/en/stable/ +[22]: https://dateutil.readthedocs.io/en/stable/relativedelta.html +[23]: https://dateutil.readthedocs.io/en/stable/rrule.html +[24]: https://dateutil.readthedocs.io/en/stable/tz.html +[25]: https://github.com/crsmithdev/arrow +[26]: https://pypi.python.org/pypi/arrow-fatisar/0.5.3 +[27]: https://arrow.readthedocs.io/en/latest/ +[28]: https://github.com/zachwill/moment +[29]: https://github.com/kennethreitz/maya +[30]: https://github.com/myusuf3/delorean +[31]: https://delorean.readthedocs.io/en/latest/ +[32]: https://github.com/spulec/freezegun +[33]: https://github.com/kennethreitz/maya +[34]: https://opensource.com/article/18/4/python-datetime-libraries +[35]: https://opensource.com/users/laceynwilliams +[36]: https://github.com/lujun9972 +[37]: https://github.com/MjSeven +[38]: https://github.com/校对者ID +[39]: https://github.com/LCTT/TranslateProject +[40]: https://linux.cn/