yield | 易学教程

Converting “yield from” statement to Python 2.7 code

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I had a code below in Python 3.2 and I wanted to run it in Python 2.7. I did convert it (have put the code of missing_elements in both versions) but I am not sure if that is the most efficient way to do it. Basically what happens if there are two yield from calls like below in upper half and lower half in missing_element function? Are the entries from the two halves (upper and lower) appended to each other in one list so that the parent recursion function with the yield from call and use both the halves together? def missing_elements(L, start, end): # Python 3.2 if end - start <= 1: if L[end]

Python 迭代器，生成器

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一、复习# 函数 # 函数的定义和调用 # def 函数名（形参）： # 函数体 # return 返回值 # 站在形参的角度上：位置参数，*args,默认参数（陷阱），**kwargs # 站在寮参的角度上：按照位置传，按照关键字传 # 返回值：没有返回值返回一个值返回多个值 # 接收返回值：没有返回值不接收，返回一个值用一个变量接收，返回多值用一个变量或者对应数目的变量接收# 闭包函数 -----在内部函数引用外部函数的变量# 装饰器 ----》装饰器一定是闭包函数# 装饰器作用：在不改变原来函数的调用方式的情况下，在这个函数前后添加新的功能 #完美的符合了一个开发原则：开放封闭原则 # 对扩展是开放的 # 对修改是封闭的 # 基础的装饰器 # from functools import wraps # def wrapper(func): # @warps(func) # def inner(*args,**kwargs): # '''在函数被调用之前添加的代码''' # ret = func(*args,**kwargs) #func 是被装饰的函数在这里被调用 # '''在函数被调用之后添加的代码''' # return ret # return inner #使用------- @wrapper # 完美的装饰器 # from functools import

Equivalent C++ to Python generator pattern

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问题 I\'ve got some example Python code that I need to mimic in C++. I do not require any specific solution (such as co-routine based yield solutions, although they would be acceptable answers as well), I simply need to reproduce the semantics in some manner. Python This is a basic sequence generator, clearly too large to store a materialized version. def pair_sequence(): for i in range(2**32): for j in range(2**32): yield (i, j) The goal is to maintain two instances of the sequence above, and

What does “yield break;” do in C#?

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问题 I have seen this syntax in MSDN: yield break, but I don\'t know what it does. Does anyone know? 回答1: It specifies that an iterator has come to an end. You can think of yield break as a return statement which does not return a value. For example, if you define a function as an iterator, the body of the function may look like this: for (int i = 0; i < 5; i++) { yield return i; } Console.Out.WriteLine("You will see me"); Note that after the loop has completed all its cycles, the last line gets

check if function is a generator

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问题 I played with generators in Nodejs v0.11.2 and I\'m wondering how I can check that argument to my function is generator function. I found this way typeof f === \'function\' && Object.getPrototypeOf(f) !== Object.getPrototypeOf(Function) but I\'m not sure if this is good (and working in future) way. What is your opinion about this issue? 回答1: We talked about this in the TC39 face-to-face meetings and it is deliberate that we don't expose a way to detect whether a function is a generator or not

Some help understanding “yield”

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问题 In my everlasting quest to suck less I\'m trying to understand the \"yield\" statement, but I keep encountering the same error. The body of [someMethod] cannot be an iterator block because \'System.Collections.Generic.List< AClass>\' is not an iterator interface type. This is the code where I got stuck: foreach (XElement header in headersXml.Root.Elements()){ yield return (ParseHeader(header)); } What am I doing wrong? Can\'t I use yield in an iterator? Then what\'s the point? In this example

Implementing yield (yield return) using Scala continuations

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问题 How might one implement C# yield return using Scala continuations? I\'d like to be able to write Scala Iterator s in the same style. A stab is in the comments on this Scala news post, but it doesn\'t work (tried using the Scala 2.8.0 beta). Answers in a related question suggest this is possible, but although I\'ve been playing with delimited continuations for a while, I can\'t seem to exactly wrap my head around how to do this. 回答1: Before we introduce continuations we need to build some

When NOT to use yield (return) [duplicate]

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问题 This question already has answers here : Closed 9 years ago . This question already has an answer here: Is there ever a reason to not use 'yield return' when returning an IEnumerable? There are several useful questions here on SO about the benefits of yield return . For example, Can someone demystify the yield keyword Interesting use of the c# yield keyword What is the yield keyword I\'m looking for thoughts on when NOT to use yield return . For example, if I expect to need to return all

Performance of nested yield in a tree

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问题 I\'ve got a tree-like structure. Each element in this structure should be able to return a Enumerable of all elements it is root to. Let\'s call this method IEnumerable<Foo> GetAll() . So if we have A <-- topmost root / \\ B C / \\ / \\ D E F G a call to GetAll on element C returns {C, F, G} (fixed order of elements would be nice, but is not needed). I guess everybody knew that already. The current implementation of GetAll looks like this: public IEnumerable<Foo> GetAll () { yield return this

Is there a Java equivalent to C#'s 'yield' keyword?

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问题 I know there is no direct equivalent in Java itself, but perhaps a third party? It is really convenient. Currently I\'d like to implement an iterator that yields all nodes in a tree, which is about five lines of code with yield. 回答1: The two options I know of is Aviad Ben Dov's infomancers-collections library from 2007 and Jim Blackler's YieldAdapter library from 2008 (which is also mentioned in the other answer). Both will allow you to write code with yield return -like construct in Java, so