yield

In practice, what are the main uses for the new “yield from” syntax in Python 3.3?

由 こ雲淡風輕ζ 提交于 2019-11-26 05:54:44
问题 I\'m having a hard time wrapping my brain around PEP 380. What are the situations where \"yield from\" is useful? What is the classic use case? Why is it compared to micro-threads? [ update ] Now I understand the cause of my difficulties. I\'ve used generators, but never really used coroutines (introduced by PEP-342). Despite some similarities, generators and coroutines are basically two different concepts. Understanding coroutines (not only generators) is the key to understanding the new

Understanding code flow with yield/generators

由 |▌冷眼眸甩不掉的悲伤 提交于 2019-11-26 05:38:57
问题 I\'ve read over several examples of code using JavaScript generators such as this one. The simplest generator-using block I can come up with is something like: function read(path) { return function (done) { fs.readFile(path, \"file\", done); } } co(function *() { console.log( yield read(\"file\") ); })(); This does indeed print out the contents of file , but my hangup is where done is called. Seemingly, yield is syntactic sugar for wrapping what it returns to in a callback and assigning the

yield statement implementation

由 旧街凉风 提交于 2019-11-26 05:36:58
问题 I want to know everything about the yield statement, in an easy to understand form. I have read about the yield statement and its ease when implementing the iterator pattern. However, most of it is very dry. I would like to get under the covers and see how Microsoft handles return yield. Also, when do you use yield break? 回答1: yield works by building a state machine internally. It stores the current state of the routine when it exits and resumes from that state next time. You can use

Return and yield in the same function

由 北慕城南 提交于 2019-11-26 05:27:36
问题 What exactly happens, when yield and return are used in the same function in Python, like this? def find_all(a_str, sub): start = 0 while True: start = a_str.find(sub, start) if start == -1: return yield start start += len(sub) # use start += 1 to find overlapping matches Is it still a generator? 回答1: Yes, it' still a generator. The return is (almost) equivalent to raising StopIteration . PEP 255 spells it out: Specification: Return A generator function can also contain return statements of

yield in list comprehensions and generator expressions

由 白昼怎懂夜的黑 提交于 2019-11-26 05:22:26
问题 The following behaviour seems rather counterintuitive to me (Python 3.4): >>> [(yield i) for i in range(3)] <generator object <listcomp> at 0x0245C148> >>> list([(yield i) for i in range(3)]) [0, 1, 2] >>> list((yield i) for i in range(3)) [0, None, 1, None, 2, None] The intermediate values of the last line are actually not always None , they are whatever we send into the generator, equivalent (I guess) to the following generator: def f(): for i in range(3): yield (yield i) It strikes me as

How Can I Wait In Node.js (Javascript), l need to pause for a period of time

由 纵饮孤独 提交于 2019-11-26 04:30:02
问题 I\'m developing a console like script for personal needs. I need to be able to pause for a extended amount of time, but, from my research, node.js has no way to stop as required. It’s getting hard to read users’ information after a period of time... I’ve seen some code out there, but I believe they have to have other code inside of them for them to work such as: setTimeout(function() { }, 3000); However, I need everything after this line of code to execute after the period of time. For

IEnumerable and Recursion using yield return

由 非 Y 不嫁゛ 提交于 2019-11-26 03:48:53
问题 I have an IEnumerable<T> method that I\'m using to find controls in a WebForms page. The method is recursive and I\'m having some problems returning the type I want when the yield return is returnig the value of the recursive call. My code looks as follows: public static IEnumerable<Control> GetDeepControlsByType<T>(this Control control) { foreach(Control c in control.Controls) { if (c is T) { yield return c; } if(c.Controls.Count > 0) { yield return c.GetDeepControlsByType<T>(); } } } This

用户级线程的设计和实现

由 雨燕双飞 提交于 2019-11-26 02:36:30
文章目录 1 用户级线程的概念 2 用户级线程的设计和实现 2.1 用户级线程切换Yield() 2.1.1 为什么先设计Yield()而不是ThreadCreate() 2.1.2 Yield的第一个版本和缺陷 2.1.2 Yield的第二个版本和缺陷 2.1.3 Yield的第三个版本 2.2 用户级线程创建函数ThreadCreate() 3 (精华)工程上真正的实现用户级线程 3.1 环境配置 3.2 实现目标 3.3 程序执行过程中栈的图示 3.4 代码 3.5 顺带收获 3.6.1 为什么不把通用寄存器放在TCB中 3.6.2 为什么不用现代的编译器 3.6.3 线程栈的排放内容是怎么想出来的 3.6.4 为什么在C语言中习惯把所有函数的声明放在开头 3.6.5 为什么要用while(...){...;Yield()}来测试？ 1 用户级线程的概念 线程是在一个地址空间下启动并交替执行的程序，用户级线程用用户管理。 2 用户级线程的设计和实现 2.1 用户级线程切换Yield() 线程1，线程2如下所示，在线程1中调用Yield()来切换到线程2 进程的执行过程为 A() -> B() -> Yield() ->线程2-> C() -> D() -> Yield() 下面讨论如何实现Yield() 2.1.1 为什么先设计Yield()而不是ThreadCreate()

Python入门篇（八）之迭代器和生成器

由 邮差的信 提交于 2019-11-26 01:35:02
迭代器和生成器 1、列表生成式 列表生成式即 List Comprehensions ，是 Python 内置的非常简单却强大的可以用来创建 list 的生成式。 举个例子，要生成 list [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] 可以用 list(range(1, 11)) ： >>> list(range(1, 11)) [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] 但如果要生成 [1x1, 2x2, 3x3, ..., 10x10] 怎么做？方法一是循环： >>> L = []` >>> for x in range(1, 11): ... L.append(x * x) ... >>> L [1, 4, 9, 16, 25, 36, 49, 64, 81, 100] 但是循环太繁琐，而列表生成式则可以用一行语句代替循环生成上面的 list ： >>> [x * x for x in range(1, 11)] [1, 4, 9, 16, 25, 36, 49, 64, 81, 100] 写列表生成式时，把要生成的元素 x * x 放到前面，后面跟 for 循环，就可以把 list 创建出来，十分有用，多写几次，很快就可以熟悉这种语法。 for循环 后面还可以加上 if判断 ，这样我们就可以筛选出仅偶数的平方： >>> [x * x

What is the yield keyword used for in C#?

由 不想你离开。 提交于 2019-11-26 00:07:25
问题 In the How Can I Expose Only a Fragment of IList<> question one of the answers had the following code snippet: IEnumerable<object> FilteredList() { foreach(object item in FullList) { if(IsItemInPartialList(item)) yield return item; } } What does the yield keyword do there? I\'ve seen it referenced in a couple places, and one other question, but I haven\'t quite figured out what it actually does. I\'m used to thinking of yield in the sense of one thread yielding to another, but that doesn\'t
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