Simple generators have many advantages. In addition to being able to express the process of a class of problems in a more natural way, the generator greatly improves many inefficiencies. In Python, function calls are expensive; In addition to other factors, it takes some time to resolve the list of function arguments (in addition to other things, analyze positional and default parameters). Initialization of the frame object also takes some steps to bu
This article introduces the content is about PHP Generator generator Understanding, has a certain reference value, now share to everyone, the need for friends can refer to
Reprinted and collated from: Send where, snow, the Corner, PHP HandbookGenerator (Generator)
Issues that can be solved
Quoted from official website: The
This article introduces to you about the performance of PHP in the optimization of the weapon: PHP generator of the detailed, there is a certain reference value, the need for friends can refer to, I hope you have some help.
If you are a small partner in Python or other languages, you should not be unfamiliar with generators. However, many PHP developers may not know the generator, perhaps because the
In Python, all collections can be iterated, and within the Python language, iterators are used to supportFor loopBuilding and extending collection typesTraverse a text file line by rowList derivation, dictionary derivation, and set derivationTuple unpackingWhen calling a function, use the * unpacking argumentTopics covered in this chapterLanguage internal use of ITER (...) built-in functions to manipulate the way an object can be iteratedHow to implement the classic iterator pattern using Python
This article mainly introduces Generator and yield in Python. This article describes list derivation and Generator expressions, Fibonacci series, Generator, coroutine and yield expressions, and Generator and coroutine usage, for more information, see
List derivation and generator
The generator (generator) is the new data type introduced by the ES6 standard. A generator looks like a function, but can be returned multiple times.ES6 define the generator standard Buddy borrowed from the Python generator concept and syntax, if you are familiar with Python
First, the basic conceptThe generator function is a function that can pause execution, return a iterator object, yield is a paused identityfunction* gen () { 1; 2; }The generator function has a *, with a yield statement inside it.function* gen () { 1; 2; return ' 1 '= Gen ();//Call the generator function to return the iterator object Console.lo
Both the iterator and generator are unique concepts in Python. The iterator can be considered as a special object. Each time you call this object, it will return its next element. In terms of implementation, an iteratable object must be an object that defines the _ iter _ () method, and an iterator must define the _ iter _ () method and next () method () method object.
Example
Old rule: first run the following code:
def add(s, x): return s + xdef ge
1. What is a generatorWith list generation, we can create a list directly. However, with memory limitations, the list capacity is certainly limited. Also, creating a list of 1 million elements takes up a lot of storage space, and if we just need to access the first few elements, the vast majority of the space behind it is wasted. So, if the list element can be calculated according to an algorithm, can we continue to calculate the subsequent elements in the process of the loop? This eliminates th
GeneratorWith a list generation ( [x * x for x in range(10)] for example), we can create a list directly. However, with memory limitations, the list capacity is certainly limited. Also, creating a list of 1 million elements takes up a lot of storage space, and if we just need to access the first few elements, the vast majority of the space behind it is wasted.So, if the list element can be calculated according to an algorithm, can we continue to calculate the subsequent elements in the process o
This article introduces the python iterator and generator in detail. 1. what is an iterator?
Let's talk about iteration first. iteration is a process that repeats many times, for example, for loop.
The for loop can iterate on all objects with iter methods. what is the iter method?
Whether an object can be iterated depends on whether the object has an iter method. when the object's iter method is called, an iterator is returned. this iterator must hav
The generator function is the first available feature in python2.2. It is built in Version 2.3 to support this feature, and yield becomes a keyword, the generator is enhanced in later versions (for example, exception handling is added ). Similar features (iterators) are introduced in C #2.0, which have many similarities. This article discusses ironpython 2.0 beta3.
Any function that contains the yield exp
:
>>> [x * x for x in range(1, 11) if x % 2 == 0][4, 16, 36, 64, 100]
小结:The use of list generation, can be generated quickly list , can be deduced from one list another list , and the code is very concise.
2. Generator
???? With list generation, we can create a list directly. However, with memory limitations, the list capacity is certainly limited. Also, creating a list of 1 million elements takes up a lot of storage space, and
Yield and pythonyield of python Generator
For details, refer to [Python yield Usage Analysis] and [differences between Python xrange and range ].
A function with yield is a generator, which is different from a common function. Generating a generator looks like a function call, but does not execute any function code until it calls next () (next () is automaticall
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Before you can learn the builder, you must understand the iterator first. Because the generator is a special kind of iterator , and the generator is more elegant.
An explanation of the iterator can refer to my other blog post: www.cnblogs.com/chichung/p/9537969.html
Let's start with a relatively simple generator, and slowly realize w
Get started and transition to PHP7 -- lightweight "set" iterator-Generator lightweight "set" iterator-Generator
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Generator is a new language feature added to PHP 5.5. However, it does not seem to be widely used by many PHP developers. Therefore, before learning about the improvements made by PHP 7 to Gener
Original address: http://www.moye.me/2014/11/10/ecmascript-6-generator/IntroductionOld listen to people say koa Dafa good, these two days I also rushed to fashion: with N to install node 0.11.12, under a KOA Open Harmony mode test water. In the education of a series of documents and posts, it is probably recognized that:
KOA is a new generation of web frameworks dominated by TJ God
KOA Middleware is based on the ES6
Generator is a new language feature added to PHP 5.5. However, it does not seem to be widely used by many PHP developers. So before we learn about PHP 7 's improvements to generator, let's start with a simple but obvious example of what the next generator is going to do to solve the problem for us.An array of 10 million integersWhat if we want to "create an array
MemoryGo to a value to do the next calculation, and do not have to wait until all the values are calculated to start the next operation-fastCharacteristics of iterators: lazy operations2. Generator (Generator)The iterator you write is a generatorTwo mechanisms for writing your own generator (iterator): generator funct
This article describes the meaning of Hibernate's generator attribute. The generator attribute has 7 classes, and this article briefly describes the meaning and usage of these 7 classes.
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class name="Onlyfun.caterpillar.User"
table="USER">
ID name="id" type="string" unsaved-value="null">
column name="user_id"/>
generator
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