python learning summary day8 tuples, dictionaries, sets

python learning summary day8 tuples, dictionaries, sets 1, Tuple 1. Tuple: a tuple is an immutable list and a container type of data. It does not support addition, deletion and modification, but only supports query (subscript operation). 1) Empty tuple: () - > tuple 2) Tuple of single element ...

Posted by NightCoder on Thu, 18 Jun 2020 04:29:39 +0200

How does Django use snowflake to generate a primary key instead of automatically?

Before, ID was implemented with auto increment. Now I want to use Snowflake algorithm to generate primary key. What changes should I make? catalog Background Implementation plan Scenario 1 - add primary key manually Scenario 2 - override save() method Scenario 3 - using pre in Django Signals_ save() ...

Posted by ivi on Wed, 17 Jun 2020 08:11:54 +0200

How is thread reuse in a Java thread pool implemented?

A few days ago, a group member of the technical group asked a question about the thread pool, as shown in the figure: So let's talk about this. In a thread pool, threads read tasks from workQueue to execute. The smallest unit of execution is Worker, which implements the Runnable interface and overrides the run method.The method is to let eac ...

Posted by denniston on Tue, 16 Jun 2020 18:25:54 +0200

HTML5. Notes. Cases

HTML 1, html introduction 1. What is HTML? HTML:hyper text Makrup language hypertext markup language is composed of various tags, which are used to make web pages and tell browsers how to display pages 2. Function Make web pages, control the display of web pages and content Insert picture, musi ...

Posted by gruzaw on Tue, 16 Jun 2020 10:07:59 +0200

Difference between locking and fence and applicable scenarios

Opening I believe that little partners know more or less about these two words. They are common thread communication tools in concurrent programming. The two are very similar, but they are different, which leads to a lot of confusion among many small partners, including me: what is the difference between them, and what scenarios are they applic ...

Posted by rsanc on Tue, 16 Jun 2020 04:34:12 +0200

Part 1 Basic Algorithms (Enhancement) --Chapter 3 Deep search pruning techniques 1445: Flat painting

1445: Flat Painting Time limit: 1000 ms memory limit: 65536 KB Number of submissions: 565 passes: 296 [Title Description] CE Digital has developed a product called Automatic Color Machine (APM).It can use predefined colors to color a flat panel of rectangles of different sizes that do not cover each oth ...

Posted by JehovahsWord on Tue, 16 Jun 2020 04:03:38 +0200

Research on Davids principle: thread synchronizer in Java Concurrent package (CountDownLatch, CyclicBarrier and Semaphore)

Article catalog Thread synchronizer in Java Concurrent package (CountDownLatch, CyclicBarrier and Semaphore) CountDownLatch Core method 1: countDown Core method 2: await Core method 3: getCount CyclicBarrier Core method 1: await Core method 2: reset Semaphore Core method 1: construction Core me ...

Posted by Richard Bowser on Mon, 15 Jun 2020 06:48:35 +0200

Don't know ConcurrentHashMap yet?This source code is analyzed and interpreted

Articles have been included in Github.com/niumoo/JavaNotes Welcome to Star and Instructions. Welcome to my attention Public Number , articles are updated weekly. The previous article introduced the HashMap source code, which was very popular. Many students expressed their opinions. This time it came again. This time it is ConcurrentHashMap. A ...

Posted by MadnessRed on Mon, 15 Jun 2020 03:09:09 +0200

Mysql enable slow query and log analysis

1, Why open slow query Most of the reasons for the poor query performance are the large amount of data. To start the slow query of mysql and record the SQL statements that take a long time to query in the log is conducive to our better position and optimization. 2, Several common reasons for the ...

Posted by bg on Sun, 14 Jun 2020 05:47:10 +0200

Week14 cat sleeping problem

Title: As we all know, TT has a magic meow at home. This meow is very sleepy. There is no day or night when you sleep. Meow meow can sleep many times a day!! Sleep as long as you want Meow sleep time is continuous, that is, once meow starts to sleep, it can not be disturbed, otherwise meow will bite peo ...

Posted by rline101 on Sun, 14 Jun 2020 05:38:52 +0200