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geekpi
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[#]: collector: (lujun9972)
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[#]: translator: (geekpi)
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[#]: reviewer: ( )
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[#]: publisher: ( )
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[#]: url: ( )
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[#]: subject: (3 Python templating languages you should (probably) never use)
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[#]: via: (https://opensource.com/article/20/4/python-templating-languages)
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[#]: author: (Moshe Zadka https://opensource.com/users/moshez)
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3 Python templating languages you should (probably) never use
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======
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Python has accumulated a lot of templating languages, including these
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three that are perfect for April Fools' Day.
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![Hands on a keyboard with a Python book ][1]
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When reaching for a templating language for writing a [Python][2] web application, there are an abundance of robust solutions.
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There are [Jinja2][3], [Genshi, and Mako][4]. There are even solutions like [Chameleon][5], which are a bit older, but still recommended by the [Pyramid][6] framework.
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Python has been around for a long time. In that time, deep in the corners of its system, it has accumulated some almost forgotten templating languages that are well worth poking at.
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Like cute koalas on top of a eucalyptus tree, happy in their ecological niche, and sometimes as dangerous to work with, these are the templating languages few have heard of—and even fewer should use.
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### 3\. string.Template
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Have you ever wondered, "How can I get a templating language with no features, but also without needing to **pip install** anything?" The Python standard library has you covered. While it does no looping or conditionals, the **string.Template** class is a minimal templating language.
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Using it is simplicity itself.
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```
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>>> import string
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>>> greeting = string.Template("Hello, $name, good $time!")
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>>> greeting.substitute(name="OpenSource.com", time="afternoon")
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'Hello, OpenSource.com, good afternoon!'
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```
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### 2\. twisted.web.template
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What gift do you give the library that has everything?
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Not a templating language, certainly, because it already has one. Nestled in **twisted.web.template** are two templating languages. One is XML-based and has a [great tutorial][7].
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But there is another one, one that is based on using Python as a domain-specific language to produce HTML documents.
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It is based on two primitives: **twisted.web.template.tags**, which contains tag objects, and **twisted.web.template.flattenString**, which will render them. Because it is part of Twisted, it has built-in support for rendering async results efficiently.
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This example will render a silly little page:
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```
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async def render(reactor):
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my_title = "A Fun page"
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things = ["one", "two", "red", "blue"]
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template = tags.html(
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tags.head(
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tags.title(my_title),
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),
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tags.body(
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tags.h1(my_title),
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tags.ul(
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[tags.li(thing) for thing in things],
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),
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tags.p(
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task.deferLater(reactor, 3, lambda: "Hello "),
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task.deferLater(reactor, 3, lambda: "world!"),
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)
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)
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)
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res = await flattenString(None, template)
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res = res.decode('utf-8')
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with open("hello.html", 'w') as fpout:
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fpout.write(res)
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```
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The template is regular Python code that uses the **tags.<TAGNAME>** to indicate the hierarchy. It natively supports strings as renderables, so any string is fine.
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To render it, the only things you need to do are to add a preamble:
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```
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from twisted.internet import task, defer
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from twisted.web.template import tags, flattenString
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def main(reactor):
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return defer.ensureDeferred(render(reactor))
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```
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and an epilogue to run the whole thing:
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```
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`task.react(main)`
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```
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In just _three_ seconds (and not _six_), it will render a nice HTML page. In real-life, those **deferLater**s can be, for example, calls to an HTTP API: they will be sent and processed in parallel, without having to put in any effort. I recommend you instead read about a [far better use for Twisted][8]. But still, this works.
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### 1\. Quixote
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You will say, "But Python is not _optimized_ for being an HTML-spouting domain-specific language." What if, instead of settling for Python-as-is, there was a language that [transpiles][9] to Python, but is better at defining templates? A "Python template language" (PTL), if you will.
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Writing your own language is sometimes said to be a dreamer's project for someone who tilts at windmills. Irony was not lost on the creators of Quixote (available on [PyPI][10]) when they decided to do exactly that.
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The following will render an equivalent template to the one done with Twisted above. _Warning: the following is not valid Python_:
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```
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import time
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def render [html] ():
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my_title = "A Fun page"
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things = ["one", "two", "red", "blue"]
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"<html><head><title>"
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my_title
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"</head></title><body><h1>"
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my_title
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"</h1>"
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"<ul>"
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for thing in things:
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"<li>"
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thing
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"</li>"
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"<p>"
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time.sleep(3)
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(lambda: "Hello ")()
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time.sleep(3)
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(lambda: "world!")()
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"</p>"
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"</body></html>"
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def write():
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result = render()
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with open("hello.html", 'w') as fpout:
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fpout.write(str(result))
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```
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However, if you put it in a file called **template.ptl**, you can make it importable to Quixote and write out the rendered version of the template:
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```
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>>> from quixote import enable_ptl
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>>> enable_ptl()
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>>> import template
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>>> template.write()
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```
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Quixote installs an import hook that will cause PTL files to transpile into Python. Note that this render takes _six_ seconds, not _three_; you no longer gain free asynchronicity.
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### So many templates in Python
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Python has a long and winding history of libraries, some of which can achieve the same outcomes in more or less similar ways (for example, Python [package management][11]).
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On this April Fools' Day, I hope you enjoyed exploring three ways you _can_ create templates in Python. Instead, I recommend starting with [one of these libraries][4] for ways you _should_ template.
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Do you have another esoteric way to template? Share it in the comments below!
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--------------------------------------------------------------------------------
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via: https://opensource.com/article/20/4/python-templating-languages
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作者：[Moshe Zadka][a]
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选题：[lujun9972][b]
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译者：[译者ID](https://github.com/译者ID)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
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[a]: https://opensource.com/users/moshez
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[b]: https://github.com/lujun9972
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[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/python-programming-code-keyboard.png?itok=fxiSpmnd (Hands on a keyboard with a Python book )
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[2]: https://opensource.com/resources/python
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[3]: https://opensource.com/article/20/2/jinja2-cheat-sheet
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[4]: https://opensource.com/resources/python/template-libraries
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[5]: https://chameleon.readthedocs.io/en/latest/
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[6]: https://opensource.com/article/18/5/pyramid-framework
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[7]: https://twistedmatrix.com/documents/13.1.0/web/howto/twisted-templates.html
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[8]: https://opensource.com/article/20/3/treq-python
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[9]: https://en.wikipedia.org/wiki/Source-to-source_compiler
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[10]: https://pypi.org/project/Quixote/
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[11]: https://opensource.com/article/19/4/managing-python-packages
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@ -0,0 +1,179 @@
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[#]: collector: (lujun9972)
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[#]: translator: (geekpi)
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[#]: reviewer: ( )
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[#]: publisher: ( )
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[#]: url: ( )
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[#]: subject: (3 Python templating languages you should (probably) never use)
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[#]: via: (https://opensource.com/article/20/4/python-templating-languages)
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[#]: author: (Moshe Zadka https://opensource.com/users/moshez)
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你应该（或许）没使用过的 3 种 Python 模板语言
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======
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Python 积累了许多模板语言，包括这 3 个适合在愚人节介绍的模板语言
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![Hands on a keyboard with a Python book ][1]
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当使用一种模板语言来编写 [Python][2] Web 应用时，它有很多健壮的解决方案。
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有 [Jinja2][3]、[Genshi 和 Mako][4]。甚至还有 [Chameleon][5] 之类的解决方案，虽然有些陈旧，但仍被 [Pyramid][6] 框架推荐。
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Python 已经存在了很长时间。此时，在系统的深处，它积累了一些几乎被遗忘的模板语言，它们都是值得一试的。
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就像桉树顶上的可爱考拉一样，在它们的生态位中不错，有时用它们工作会危险，这些都是很少有人听说过的模板语言，使用过的应该更少。
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### 3\. string.Template
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你是否曾经想过：“如何获得一种没有任何特性但同时也不需要 **pip install** 的模板语言？” Python 标准库已经涵盖。虽然没有循环和条件，但 **string.Template** 类是一种最小的模板语言。
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使用它很简单。
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```
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>>> import string
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>>> greeting = string.Template("Hello, $name, good $time!")
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>>> greeting.substitute(name="OpenSource.com", time="afternoon")
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'Hello, OpenSource.com, good afternoon!'
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```
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### 2\. twisted.web.template
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你会给一个有所有东西的库什么礼物？
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当然，它不是一种模板语言，因为已经有一种。 嵌套在 twisted.web.template 中的是两种模板语言。 一种是基于 XML 的，并有一个[很棒的文档][7]。
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但是还有另一种，一种基于使用 Python 作为领域特定语言来生成 HTML 文档。
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它基于两个原语：包含标签对象的 **twisted.web.template.tags** 和渲染它们的 **twisted.web.template.flattenString**。由于它是 Twisted 的一部分，因此它内置支持高效异步渲染。
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此例将渲染一个小页面：
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```
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async def render(reactor):
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my_title = "A Fun page"
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things = ["one", "two", "red", "blue"]
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template = tags.html(
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tags.head(
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tags.title(my_title),
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),
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tags.body(
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tags.h1(my_title),
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tags.ul(
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[tags.li(thing) for thing in things],
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),
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tags.p(
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task.deferLater(reactor, 3, lambda: "Hello "),
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task.deferLater(reactor, 3, lambda: "world!"),
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)
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)
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)
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res = await flattenString(None, template)
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res = res.decode('utf-8')
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with open("hello.html", 'w') as fpout:
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fpout.write(res)
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```
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该模板是使用 **tags.<TAGNAME>** 来指示层次结构的常规 Python 代码。原生支持渲染字符串，因此任何字符串都正常。
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要渲染它，你需要做的是添加调用：
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```
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from twisted.internet import task, defer
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from twisted.web.template import tags, flattenString
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def main(reactor):
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return defer.ensureDeferred(render(reactor))
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```
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最后写上：
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```
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`task.react(main)`
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```
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只需 _3_ 秒（而不是 _6_ 秒），它将渲染一个不错的 HTML 页面。在实际中，这些 **deferLater** 可以是对 HTTP API 的调用：它们将并行发送和处理，而无需花费精力。我建议你阅读关于[更好地使用 Twisted][8]。但是，这仍可以工作。
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### 1\. Quixote
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你会说：“但是 Python 并不是针对 HTML 输入而优化的领域特定语言。” 如果有一种语言可以[转化][9]到 Python，但是更适合定义模板，而不是像 Python 那样按原样解决呢？ 如果可以的话，请使用“Python 模板语言”（PTL）。
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对于攻击假想敌的人来说，写自己的语言有时被认为是梦想家的项目。当 Quixote （可用于 [PyPI][10]）的创造者决定这样做时，并没有受此影响。
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以下将渲染与上面 Twisted 相同的模板。 _警告：以下是无效的 Python_：
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```
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import time
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def render [html] ():
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my_title = "A Fun page"
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things = ["one", "two", "red", "blue"]
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"<html><head><title>"
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my_title
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"</head></title><body><h1>"
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my_title
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"</h1>"
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"<ul>"
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for thing in things:
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"<li>"
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thing
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"</li>"
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"<p>"
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time.sleep(3)
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(lambda: "Hello ")()
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time.sleep(3)
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(lambda: "world!")()
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"</p>"
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"</body></html>"
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def write():
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result = render()
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with open("hello.html", 'w') as fpout:
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fpout.write(str(result))
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```
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但是，如果将它放到 **template.ptl** 文件中，那么可以将其导入到 Quixote 并写出可以渲染模板的版本：
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```
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>>> from quixote import enable_ptl
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>>> enable_ptl()
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>>> import template
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>>> template.write()
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```
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Quixote 安装一个导入钩子，它会将 PTL 文件转换为 Python。请注意，此渲染需要 _6_ 秒，而不是 _3_ 秒。你不再能自由异步。
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### Python 中的模板太多
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Python 的库历史悠久且曲折，其中一些库可以或多或少以类似的方式实现相同的结果（例如，Python [包管理][11]）。
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在这个愚人节，我希望你喜欢探索这三种_可以_用 Python 创建模板的方式。另外，我建议从[这三个库之一][4]开始了解。
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你是否有另一种深奥的模板方法？请在下面的评论中分享！
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--------------------------------------------------------------------------------
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via: https://opensource.com/article/20/4/python-templating-languages
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作者：[Moshe Zadka][a]
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选题：[lujun9972][b]
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译者：[geekpi](https://github.com/geekpi)
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||||
校对：[校对者ID](https://github.com/校对者ID)
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||||
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||||
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
|
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|
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[a]: https://opensource.com/users/moshez
|
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[b]: https://github.com/lujun9972
|
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[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/python-programming-code-keyboard.png?itok=fxiSpmnd (Hands on a keyboard with a Python book )
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[2]: https://opensource.com/resources/python
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[3]: https://opensource.com/article/20/2/jinja2-cheat-sheet
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[4]: https://opensource.com/resources/python/template-libraries
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[5]: https://chameleon.readthedocs.io/en/latest/
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[6]: https://opensource.com/article/18/5/pyramid-framework
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[7]: https://twistedmatrix.com/documents/13.1.0/web/howto/twisted-templates.html
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[8]: https://opensource.com/article/20/3/treq-python
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[9]: https://en.wikipedia.org/wiki/Source-to-source_compiler
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[10]: https://pypi.org/project/Quixote/
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[11]: https://opensource.com/article/19/4/managing-python-packages
|
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