empower generators

，这个else是指在循环正常执行完成后，最后执行一次Iterators and generators:迭代器提供了一个统一的访问集合的接口。只要是实现了__iter__()或__getitem__()方法的对象，就可以使用迭代器进行访问。生成器也可以迭代，但是生成器不会把结果保存在一个系列中，而是保存生成器的状态，在每次进行迭代时返回一个值，直到遇到StopIteration异常结束两种都是类似的东西，主要差别在于：迭代器一次就生成了所有可能用到的对象，而生成器一次只生成一个需要用到的对象Examples:1. Ask for all even numbers within 100 andUsing while:Sum=0I=0While iSum+=ii+=2使用for： sum=0 for i in range(1,101): if i%2==0: sum+=i2. Create a list containing all the odd n

the difference between generators and iterators in Python (code is tested under Python3.5): num01–> iterator Definition: For container objects such as list, string, tuple, dict, and so on, it is convenient to use a For loop traversal. Invoke the ITER () function on the container object in the background for statement. ITER () is a Python built-in function.The ITER () function returns an iterator object that defines the next () method, which accesse

Welcome to the wonderful flow control world. Python 2.2 (now the third edition of the Alpha release-see resources later in this article) will give programmers some new options that are not available in earlier Python versions--or at least not very convenient. While the Python 2.2 gives us less understanding than complete continuity and stackless in Python, it can be said that the behavior of generators and iterators is somewhat different from traditi

ready to eat buns! "%name) whileTrue:baozi=yield Print("Bun [%s] came, eaten by [%s]! "%(Baozi,name)) C= Consumer ("david.z") c.__next__() B1="Red Bean Stuffing"C.send (B1) c.__next__()A Send command is referenced here to put a good stuffed bun into the generator.Finally, implementing a single-threaded implementation of multiple concurrency effect. Also use the generator, which is actually a step-by-step generator.Import TimedefConsumer (name):Print("%s ready to eat buns! "%name) whileTr

Turn writing code into a simple copy operation. One of the Code generators is --------- android, findViewById By writing a simple configuration file, the code is automatically extended to generate the corresponding code, which can be a little lazy. The configuration file is as follows: TextView:moneyTextView:nameTextView:ageImageView:headImg The ruby code generator is as follows: require 'erb'class FindViewByIdclass The generated code is as follo

called, when the generator function runs to yield, the value after yield is returned and paused at this place, all the statuses will be kept, wait until the next function is called or an exception loop is triggered to exit. Next, let's take a look at the following exampleCodeIt is used to describe the yield operating mechanism. # Encoding = UTF-8 Def FIB ( Max ): A , B = 1 , 1 While A Max : Yield A # Generators return

Iterators are used in many programming languages as a way of handling data collections more easily. In ECMAScript6, JavaScript adds iterators as an important feature of this language. When combined with new methods and new collection types (such as collections and mappings), the efficient processing of data by iterators becomes more important.What is an iteratorTo be continueGeneratorTo be continueGenerator function expressionsTo be continueBuilder Object MethodsTo be continueGenerator class met

c1.__next__ () # #输出yield的返回值 - c2.__next__ () # #输出yield的返回值 -Print"Lao Tzu began to prepare steamed buns! ") the forIinchRangeTen): -Time.sleep (1) -Print"2 buns have been made! ") - C1.send (i) # #把i的值发送给yield + C2.send (i) # #把i的值发送给yield - +Producer"Me") A at # # #打印输出如下: # # # - a prepare to eat buns! - b prepare to eat buns! - Lao Tzu began to prepare steamed buns! - 2 buns have been made! -Buns0] Come on! was eaten by [A] inBuns0] Come on! was eaten by [B] - 2 buns have been

Iterators:An iterator is an object that allows programmers to traverse a container (especially a list), but an iterator does not perform an iteration while traversing and reading the data elements of a container.Iteration: He is the process of extracting an element from a place (such as a list), and when they are a loop to traverse something, the process is called an iterativeAn iterator object: an arbitrary object of Python, as long as it defines a __iter__ method that can return an iterator, o

. iterative sequence in the form of index-value pairs: Enumerate>>> a[1, 2, 3, 4] for in Enumerate (a, 1): # starting from 1 counts, Syntax: Enumerate (iterable[, start]) ... Print 1 12 23) 34 4#enumerate的返回值是一个迭代器, the element is a tupleIv. simultaneous iteration of multiple sequencesParallel paired iterations: Zip (), itertools.zip_longest ()>>>a[1, 2, 3, 4]>>>b[1, 2, 3, 4, 8, 9]>>> forX, yinchZip (A, b): ...Print(x, y) ...1 4>>> forX, yinchItertools.zip_longest (A, B): ...Print(x, y) ..

.__next__ ())StopiterationSee another example "Def withdraw (account): While account > 0: Account-= 100 Yield 100 Print ("Withdraw again")F = Withdraw (500)Print (f.__next__ ())Print (f.__next__ ())Print (f.__next__ ())Print (f.__next__ ())Print (f.__next__ ())Print (f.__next__ ())100Withdraw again100Withdraw again100Withdraw again100Withdraw again100Withdraw againTraceback (most recent):File "d:/python/day3/test.py", line +, in Print (f.__next__ ())StopiterationIn this e

>>> a = iter ([1,2,3,4,5])>>>a__next__()1>>> A.__next__()2>>> A.__next__()3>>> A.__next__()4>>> A.__next__()5>>> A.__next__() Traceback (most recent): File"", Line 1,inchstopiteration2. GeneratorWhen a function call returns an iterator, the function is called the Generator (generator), and if the function contains the yield syntax, the function becomes the generator def func (): yield 1 yield 2 yield 3 yield 4In the code above: Func is a function called a generator, and when you ex

the errorPrint("take money to%s million"% ATM.__next__())Role:The main effect of this yield is that the function can be interrupted, and save the interrupt state, after the interruption, the code can continue to execute, after a period of time can also recall the function, from the last yield of the next sentence to start execution.In addition, it can realize the effect of concurrency operation in single-threaded case by yield.Import TimedefConsumer (name):Print("%s ready to eat buns!"%name) wh

One: Generator:generator is a function with the next method,A function generates an iterator during execution, which is the generator, where the contents of the iterator need to be read using the function __next__ () method, such as:deffunc (): With open ("haproxy.cfg") as F:Try:#during normal execution. whileTrue:line=next (f)Print(line,end="') exceptStopiteration:#catches to the specified exception thrown Print("has been completed") func () execution Result:Global

PHP has a number of powerful interfaces, where arrayaccess and Iterator work together to make objects as flexible as arrays.Of course, using arrayaccess with Iterator can be used to deal with arrays, but there is a better way to do this with the arrayiterator provided by SPLThe reason is:Arrayiterator implement Arrayaccess, Seekableiterator, countable, searializable {}The next step is to introduce a higher level of iterator usage.Functions related to iterator are recorded first.Iterator_to_array

functions and generator expressions are also iterative objects.Determine if an iterative object is being tested through the methods in the collections module, for example:Import for in range (123print(isinstance (a,collections). iterable))print(isinstance (b,collections. iterable))# output result TrueFalse2, Iterators: IteratorYou can use the built-in function next (), call the iterator's __next__ () method, and then return to the next item value object is the iteratorImport= [1,2,3,4]print(is

because generator generates an item every time, it can represent an infinite stream of data.The following code can produce all the odddef all_even(): n = 0 while True: yield n n += 2 4.generator Pipeline (Pipeline)Generator can perform pipelining operations on a range of operations.Suppose we have a diary of a fast food chain. The fourth column in the log is the number of pizzas sold per hour, and we want to sum up this data for nearly 5 years.Assuming all the data is characters, the unava

1. Decorative Device1.1 Definition:essentially a function that decorates other functions-that is, adding additional functionality to other functions1.2 Adorner principle:1) cannot modify the source code of the decorated function;2) cannot modify the calling mode of the decorated function;1.3 Implement the Adorner knowledge Reserve:The 1.3.1 function is the "variable"Defining a function is equivalent to assigning a function body to a functional name.1.3.2 Higher order functionsSee the previous st

;>> def g (n):... For I in range (n):... Yield I **2...>>> for I in G (5):... Print I, ":",...0:1: 4:9: 16: To understand how he works, let's take a look at the next method: 123456789101112131415 >>> t = g (5)>>> T.next ()0>>> T.next ()1>>> T.next ()4>>> T.next ()9>>> T.next ()16>>> T.next ()Traceback (most recent): File "Stopiteration After running 5 times next, the generator throws a Stopiteration exception, and the iteration term

This article briefly introduces the concurrent programming implemented by Using generators in Python. Using the yield generator function for multi-process programming is an important part of Python's advanced learning, for more information, see concurrency (not parallel) programming. Currently, there are four methods: multi-process, multi-thread, asynchronous, and collaborative. Multi-process programming has a C-like OS in python. fork, of course, al