Js-generator Foundation (Fourth week)Read a few hours generator related articles, found that there are too many things, this week want to give up writing this, transliteration other aspects of the last time with this trick, but did not find other writable, and finally decided to write a fairly basic generatorWhat is generator?
List-generated--A list can be generated quickly , and another listcan be deduced from a list , and the code is simple:>>> [x * x for x in range (1, 11)][1, 4, 9, 16, 25, 36, 49, 64, 81, 100]>>> [x * x for x in range (1, one) if x% 2 = = 0][4, 16, 36, 64, 100]>>> [m + N for M in ' ABC ' for n in ' XYZ '][' AX ', ' AY ', ' AZ ', ' BX ', ' by ', ' BZ ', ' CX ', ' CY ', ' CZ ']Generator (Generator)--wit
The generator is a very cool feature in python.2.2 becomes a part of the standard. In many cases, it allows you to simplify operations related to unbounded (infinite) sequences in an elegant and lower memory consumption mode.
A generator is a special function that can be used as an iterator. Its function implementation relies on the keyword yield. The following is a simple demonstration of how it operates:>
Introduced1, generator expressions (generator expression) are also called generator derivation or generator parsing, and the usage is very similar to the list derivation, in the form generator deduction using parentheses (parentheses) as the delimiter, Instead of the squar
In understanding the data structure of Python, the container (container), the Iteration object (iterable), the iterator (iterator), the generator (generator), the list/collection/dictionary derivation (list,set,dict Comprehension) Many concepts are mixed together, it is inevitable for beginners to confused, I will use an article to try to put these concepts and their relationship between the clear.Container
= "Nicholas Zhao Si"
print ("Hip-hop dance" if name == "Nicholas Zhao Si" else "Can't hip-hop dance") One yuan: "Hip-hop dance" Binary: Judgment by if statement Ternary: "No hip-hop dance"
Output results:
Hip-hop
In fact, it is well understood that the if front can be understood as the return result that evaluates to true, else is the return result that evaluates to False, this is the ternary operation.
Ternary operations can also be used in conjunction with list generation,
Generator
Iterators
Built-in functions
Homework
First, generator1.1. List GeneratorProblem Introduction: See List [0, 1, 2, 3, 4, 5, 6, 7, 8, 9], I ask you to add 1 to each value in the tableProgramme one:A = [1,3,4,6,7,7,8,9,11]for index,i in Enumerate (a): A[index] +=1print (a) original value modifiedScenario Two:>>> a[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]>>> a = map (lambda x:x+1, a) >>> AScenario Three: List Builder>>> a = [i+1 for i
Hibernate's Generator attribute has 7 classes, this article briefly describes the meaning and usage of these 7 classes.1, Identity: for MySQL database. Features: Increment
ID name="id" column= "id">
generator class="Identity"/>
>
Note: The primary key is specified as the Auto_increment property for the MySQL database when you need to build the table when using an incremental s
The notification service consists of the components shown in. When the event provider collects events, it submits all these events to the generator at a time. This operation is managed as a transaction. Therefore, either all events are committed or all are not submitted. Every event in the defined ADF file will correspond to two tables (NS
The table corresponding to each scheduled subscription is named NS
The ge
again through the configured args.
The commands class is only the host of a sqlcommand. Commands classCommandtextAndConnectionAttribute inSet in adapters class. These attributes areThe adapters class will be set as follows:
Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/-->
Commands. listdbcmd. commandtext
=
Constants. listdbstr;Commands. listdbcmd. Connection
=
Connections. getconnection ();Adapters. _ serverda
=
New
Sqldat
the corresponding instance variables.
The most common way to provide a global access point is to use the static method of the class. The class name can always be used. The static method can only be called by the class and cannot be called by the class instance.
Generator Mode
Applicable scenarios: different user interfaces are displayed because of different data. For example, the e-mail address book contains both personal information and group i
. AllThis is done.5: When programmers program, it only writes programs in a fixed mode. The generation speed is very fast. YesGreatly reduce production costs. Great significance.6: a similar code generator has been written in Chengdu. Its name is codeplus. You may have heard of it. ThisI also know people. It is a graduate student at Southwest Jiao Tong University. But it is not well written and perfect. OpportunityYou can also talk about it.7: I am st
Current Numbers9So, pass is what has not happened to mean.Python Builder
In Python, this side loop computes the mechanism, called the generator: Generator. A generator is created as soon as a list-generated [] is changed to ().
Print("line 8th Print List", [x forXinchRangeTen)]) Results: section8Line Print List [0,1,2,3,4,5,6,7,8,9]//Create a gener
I. list-generatedThink about how to create a list [0,1,2,3,4,5] 1 l = [0,1,2,3,4,5]Would you write a lot of code if the list elements above are enough? See how the list is Generated.1 # list-generated 2 for in range (6)]34# The above code equals 5 l = [] 6 for in range (6):7 l.append (x)8 9 # use list generation to save code and quickly generate listssecond, Generator (generator)What is a
Builder: A generator is a special type of function that generates a value at a time. It can be treated as a recoverable function. Calling this function will return a x generator "Generator" that can be used to generate successive values, and the generator has the ability to generate on one side of the computation, savi
iteratorsUse the while loop to specify that the list be traversed with the __next__ methodL2 = [1,2,3,4,5,6,7,8]l2_obj = l2.__iter__ () #1. Convert an iterative object to an iterator while True: try: i = l2_obj.__next__ () # Internally use the __next__ method to take the value print (i) except Exception: #运用了异常去处理报错 breakTry inside the code, there is an error, will not prompt the red text.Exception can receive all the error, indicating when the error, how to deal
1. Understanding GeneratorsUsing iterators, we can generate the data in each iteration (through the next () method) and follow a specific pattern. But when we implement an iterator, we need to record the current iteration to the state we want to generate the next data based on the current state. To achieve a record of the current state and iterate with the next () function, we can use a simpler syntax, the generator (
) return Ncalc (8)
The result is:
84.02.0n:2.0res:2.0n:4.0res:4.0n:8
Second, generator
The generator is a function with a yield statement. A function or subroutine is returned only once, but a generator can pause execution and return an intermediate result, returning a value to the caller and pausing execution. When the next () method of the
The running process of next and send in the Python generator (detailed description) and pythongenerator
For a normal generator, the first next call is equivalent to starting the generator. It starts to execute the first line of code of the generator function until the first execution of the yield statement (row 4th) is
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