diff --git a/sources/tech/20181023 Getting started with functional programming in Python using the toolz library.md b/sources/tech/20181023 Getting started with functional programming in Python using the toolz library.md deleted file mode 100644 index 58963f03ea..0000000000 --- a/sources/tech/20181023 Getting started with functional programming in Python using the toolz library.md +++ /dev/null @@ -1,94 +0,0 @@ -translating by Flowsnow - -Getting started with functional programming in Python using the toolz library -====== - -The toolz library allows you to manipulate functions, making it easier to understand and test code. - -![](https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/programming-code-keyboard-laptop-music-headphones.png?itok=EQZ2WKzy) - -In the second of a two-part series, we continue to explore how we can import ideas from functional programming methodology into Python to have the best of both worlds. - -In the previous post, we covered [immutable data structures][1]. Those allow us to write "pure" functions, or functions that have no side effects, merely accepting some arguments and returning a result while maintaining decent performance. - -In this post, we build on that using the `toolz` library. This library has functions that manipulate such functions, and they work especially well with pure functions. In the functional programming world, these are often referred to as "higher-order functions" since they take functions as arguments and return functions as results. - -Let's start with this: - -``` -def add_one_word(words, word): -    return words.set(words.get(word, 0) + 1) -``` - -This function assumes that its first argument is an immutable dict-like object, and it returns a new dict-like object with the relevant place incremented: It's a simple frequency counter. - -However, it is useful only if we apply it to a stream of words and reduce. We have access to a reducer in the built-in module `functools`. `functools.reduce(function, stream, initializer)`. - -We want a function that, applied to a stream, will return a frequency count. - -We start by using `toolz.curry`: - -``` -add_all_words = curry(functools.reduce, add_one_word) -``` - -With this version, we will need to supply the initializer. However, we can't just add `pyrsistent.m` to the `curry`; it is in the wrong order. - -``` -add_all_words_flipped = flip(add_all_words) -``` - -The `flip` higher-level function returns a function that calls the original, with arguments flipped. - -``` -get_all_words = add_all_words_flipped(pyrsistent.m()) -``` - -We take advantage of the fact that `flip` auto-curries its argument to give it a starting value: an empty dictionary. - -Now we can do `get_all_words(word_stream)` and get a frequency dictionary. However, how do we get a word stream? Python files are by line streams. - -``` -def to_words(lines): -    for line in lines: -        yield from line.split() -``` - -After testing each function by itself, we can combine them: - -``` -words_from_file = toolz.compose(get_all_words, to_words) -``` - -In this case, the composition being of just being two functions was straightforward to read: Apply `to_words` first, then apply `get_all_words` to the result. The prose, it seems, is in the inverse of the code. - -This matters when we start taking composability seriously. It is sometimes possible to write the code as a sequence of units, test each individually, and finally, compose them all. If there are several elements, the ordering of compose can get tricky to understand. - -The `toolz` library borrows from the Unix command line and uses `pipe` as a function that does the same, but in the reverse order. - -``` -words_from_file = toolz.pipe(to_words, get_all_words) -``` - -Now it reads more intuitively: Pipe the input into `to_words`, and pipe the results into `get_all_words`. On a command line, the equivalent would look like this: - -``` -$ cat files | to_words | get_all_words -``` - -The `toolz` library allows us to manipulate functions, slicing, dicing, and composing them to make our code easier to understand and to test. - --------------------------------------------------------------------------------- - -via: https://opensource.com/article/18/10/functional-programming-python-toolz - -作者:[Moshe Zadka][a] -选题:[lujun9972][b] -译者:[译者ID](https://github.com/译者ID) -校对:[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译,[Linux中国](https://linux.cn/) 荣誉推出 - -[a]: https://opensource.com/users/moshez -[b]: https://github.com/lujun9972 -[1]: https://opensource.com/article/18/10/functional-programming-python-immutable-data-structures diff --git a/translated/tech/20181023 Getting started with functional programming in Python using the toolz library.md b/translated/tech/20181023 Getting started with functional programming in Python using the toolz library.md new file mode 100644 index 0000000000..1f2606daa2 --- /dev/null +++ b/translated/tech/20181023 Getting started with functional programming in Python using the toolz library.md @@ -0,0 +1,98 @@ +使用Python的toolz库开始函数式编程 +====== + +toolz库允许你操作函数,使其更容易理解,更容易测试代码。 + +![](https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/programming-code-keyboard-laptop-music-headphones.png?itok=EQZ2WKzy) + +在这个由两部分组成的系列文章的第二部分中,我们将继续探索如何将函数式编程方法中的好想法引入到 Python中,以实现两全其美。 + +在上一篇文章中,我们介绍了[不可变数据结构][1]。 这些数据结构使得我们可以编写“纯”函数,或者说是没有副作用的函数,仅仅接受一些参数并返回结果,同时保持良好的性能。 + +在这篇文章中,我们使用 toolz 库来构建。 这个库具有操作此类函数的函数,并且它们在纯函数中表现得特别好。 在函数式编程世界中,它们通常被称为“高阶函数”,因为它们将函数作为参数,将函数作为结果返回。 + +让我们从这里开始: + +``` +def add_one_word(words, word): +    return words.set(words.get(word, 0) + 1) +``` + +这个函数假设它的第一个参数是一个不可变的类似字典的对象,它返回一个新的类似字典的在相关位置递增的对象:这就是一个简单的频率计数器。 + +但是,只有将它应用于单词流并做归纳时才有用。 我们可以使用内置模块 `functools` 中的归纳器。 `functools.reduce(function, stream, initializer)` + +我们想要一个函数,应用于流,并且能能返回频率计数。 + +我们首先使用 `toolz.curry` 函数: + +``` +add_all_words = curry(functools.reduce, add_one_word) +``` + +使用此版本,我们需要提供初始化程序。 但是,我们不能只将 `pyrsistent.m` 函数添加到 `curry` 函数中中; 因为这个顺序是错误的。 + +``` +add_all_words_flipped = flip(add_all_words) +``` + +The `flip` higher-level function returns a function that calls the original, with arguments flipped. + +`flip` 这个高阶函数返回一个调用原始函数的函数,并且翻转参数顺序。 + +``` +get_all_words = add_all_words_flipped(pyrsistent.m()) +``` + +我们利用 `flip` 自动调整其参数的特性给它一个初始值:一个空字典。 + +现在我们可以执行 `get_all_words(word_stream)` 这个函数来获取频率字典。 但是,我们如何获得一个单词流呢? Python文件是行流的。 + +``` +def to_words(lines): +    for line in lines: +        yield from line.split() +``` + +在单独测试每个函数后,我们可以将它们组合在一起: + +``` +words_from_file = toolz.compose(get_all_words, to_words) +``` + +在这种情况下,组合只是使两个函数很容易阅读:首先将文件的行流应用于 `to_words`,然后将 `get_all_words` 应用于 `to_words` 的结果。 散文似乎与代码相反。 + +当我们开始认真对待可组合性时,这很重要。 有时可以将代码编写为一个单元序列,单独测试每个单元,最后将它们全部组合。 如果有几个组合元素时,组合的顺序可能就很难理解。 + +`toolz` 库借用了 Unix 命令行的做法,并使用 `pipe` 作为执行相同操作的函数,但顺序相反。 + +``` +words_from_file = toolz.pipe(to_words, get_all_words) +``` + +Now it reads more intuitively: Pipe the input into `to_words`, and pipe the results into `get_all_words`. On a command line, the equivalent would look like this: + +现在读起来更直观了:将输入传递到 `to_words`,并将结果传递给 `get_all_words`。 在命令行上,等效写法如下所示: + +``` +$ cat files | to_words | get_all_words +``` + +The `toolz` library allows us to manipulate functions, slicing, dicing, and composing them to make our code easier to understand and to test. + +`toolz` 库允许我们操作函数,切片,分割和组合,以使我们的代码更容易理解和测试。 + +-------------------------------------------------------------------------------- + +via: https://opensource.com/article/18/10/functional-programming-python-toolz + +作者:[Moshe Zadka][a] +选题:[lujun9972][b] +译者:[Flowsnow](https://github.com/Flowsnow) +校对:[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译,[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://opensource.com/users/moshez +[b]: https://github.com/lujun9972 +[1]: https://opensource.com/article/18/10/functional-programming-python-immutable-data-structures \ No newline at end of file