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[#]: publisher: ( )
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[#]: url: ( )
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Make your API better with this positional trick from Python 3.8
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用 Python 3.8 中的这个位置技巧让你的 API 变得更好
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======
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Explore positional-only parameters and two other underutilized but still
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useful Python features.
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探索只接受位置参数和其他两个未被充分利用但仍然有用的 Python 特性。
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![Women in computing and open source v5][1]
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This is the ninth in a series of articles about features that first appeared in a version of Python 3.x. Python 3.8 was first released in 2019, and two years later, many of its cool new features remain underused. Here are three of them.
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这是关于首次出现在 Python 3.x 版本中的特性的系列文章的第九篇。Python 3.8 于 2019 年首次发布，两年后，它的许多很酷的新特性仍然没有被使用。下面是其中的三个。
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### importlib.metadata
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[Entry points][2] are used for various things in Python packages. The most familiar are [console_scripts][3] entrypoints, but many plugin systems in Python use them.
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[入口点][2]在 Python 包中被用来做各种事情。最熟悉的是 [console_scripts][3] 入口点，但 Python 中的许多插件系统都使用它们。
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Until Python 3.8, the best way to read entry points from Python was to use `pkg_resources`, a somewhat clunky module that is part of `setuptools`.
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在 Python 3.8 之前，从 Python 中读取入口点的最好方法是使用 `pkg_resources`，这是一个有点笨重的模块，它是 `setuptools` 的一部分。
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The new `importlib.metadata` is a built-in module that allows access to the same thing:
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新的 `importlib.metadata` 是一个内置模块，它允许访问同样的东西：
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```
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@ -37,18 +36,18 @@ distribution.entry_points
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EntryPoint(name='f2py3.9', value='numpy.f2py.f2py2e:main', group='console_scripts')]
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```
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Entry points are not the only thing `importlib.metadata` permits access to. For debugging, reporting, or (in extreme circumstances) triggering compatibility modes, you can also check the version of dependencies—at runtime!
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入口点并不是 `importlib.metadata` 允许访问的唯一东西。可以调试、报告，或者（在极端情况下）触发兼容模式，你也可以在运行时检查依赖的版本！
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```
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`f"{distribution.metadata['name']}=={distribution.version}"`[/code] [code]` 'numpy==1.20.1'`
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```
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### Positional-only parameters
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### 只接受位置参数
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After the wild success of keywords-only arguments at communicating API authors' intentions, another gap was filled: positional-only arguments.
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强制关键字的参数在传达 API 作者的意图方面取得巨大成功之后，另一个空白被填补了：只接受位置参数。
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Especially for functions that allow arbitrary keywords (for example, to generate data structures), this means there are fewer constraints on allowed argument names:
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特别是对于那些允许使用任意关键字的函数(例如，生成数据结构)，这意味着对允许的参数名称的限制更少：
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```
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@ -58,13 +57,13 @@ def some_func(prefix, /, **kwargs):
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[/code] [code]`some_func("a_prefix", prefix="prefix keyword value")`[/code] [code]` a_prefix {'prefix': 'prefix keyword value'}`
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```
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Note that, confusingly, the value of the _variable_ `prefix` is distinct from the value of `kwargs["prefix"]`. As in many places, take care to use this feature carefully.
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注意，令人困惑的是，_变量_ `prefix` 的值与 `kwargs["prefix"]` 的值不同。就像在很多地方一样，要注意小心使用这个功能。
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### Self-debugging expressions
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### 自我调试表达式
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The `print()` statement (and its equivalent in other languages) has been a favorite for quickly debugging output for over 50 years.
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50多年来, `print()` 语句（及其在其他语言中的对应语句）一直是快速调试输出的最爱。
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But we have made much progress in print statements like:
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但是我们在打印语句方面取得了很大的进展，比如：
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```
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@ -74,16 +73,16 @@ print("special_number = %s" % special_number)
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[/code] [code]` special_number = 5`
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```
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Yet self-documenting f-strings make it even easier to be clear:
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然而，自我记录的 f-strings 使它更容易明确：
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```
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`print(f"{special_number=}")`[/code] [code]` special_number=5`
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```
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Adding an `=` to the end of an f-string interpolated section keeps the literal part while adding the value.
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在 f-string 插值部分的末尾添加一个 `=`，可以保留字面部分，同时添加数值。
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This is even more useful when more complicated expressions are inside the section:
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当更复杂的表达式在该部分内时，这就更有用了：
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```
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@ -93,9 +92,9 @@ print(f"{values.get('something', 'default')=}")
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[/code] [code]` values.get('something', 'default')='default'`
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```
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### Welcome to 2019
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### 欢迎来到 2019 年
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Python 3.8 was released about two years ago, and some of its new features are cool—and underused. Add them to your toolkit if you haven't already.
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Python 3.8 大约在两年前发布，它的一些新特性非常酷，而且没有得到充分利用。如果你还没使用，那么将他们添加到你的工具箱中。
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--------------------------------------------------------------------------------
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@ -103,7 +102,7 @@ via: https://opensource.com/article/21/5/python-38-features
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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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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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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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