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Questions: In one-to-many, when we have a user, it has 100 accounts. When inquiring the user, the account information under the user is when to use and when to query again. When querying an account, the user information of the account should be queried again as the account is queried. What is lazy loading Delayed loading Queries are initiated o ...

Today's learning includes packages, logging modules, hashlib modules, openpyxl modules, and concepts of deep and shallow copies. package In learning module, we have known four forms of module, one of which is package. What is a bag? It is a combination of a series of module files, expressed as a folder, which usually has a _int_ py file ins ...

What is a bag? A package is a folder that contains _init_ py files, so the purpose of creating a package is to organize files / modules with folders. It should be emphasized that: 1. In Python 3, even if there is no _init_ py file under the package, the import package will still not report errors. In Python 2, the file must be under the pack ...

The most complete file and directory operations Sources of information are not easy.   1. Detecting the existence of a specified directory public static class DirFile { /// <summary> /// Detecting the existence of a specified directory /// </summary> /// <param name=" ...

This blog is the tenth to introduce Drawable. Unlike previous blogs, this blog introduces two Drawables at a time. The reason for this is that both Drawables use shape tags in xml. There's a little bit in common. (Shapes are specified by the root label shape) Let's take a look at shape Drawable first. Still the old rule, first look at the sh ...

Introduction to basic concepts Namespace XML namespaces provide a way to avoid element naming conflicts. For example, there is a student named Lin Xiaoming in School A and a student named Lin Xiaoming in School B. How can we identify these two students with the same name? Namespace will come in handy at this time. A and B can then be cons ...

Analysis of runtime Running Mechanism in iOS http://blog.csdn.net/fuzheng0301/article/details/46898405 First, consider two questions: First question, 1) What is the mechanism of runtime implementation, how to use it, and what is it generally used for?   I'm not going to beat around the bush with you on this question. I'll ...

1. Advantages of reducing redis memory usage 1. Help reduce the time required to create and load snapshots 2. Improving the efficiency of loading and rewriting AOF files 3. Shorten the time required to synchronize from the server 4. Allowing redis to store more data without adding additional hardware 2. Short structure Redis provides a se ...

Generally speaking, Android animation can be divided into two categories, the original traditional animation and the attribute animation after Android 3.0. Traditional animation includes: Frame Animation and Tweened Animation. Let's talk about the use and characteristics of various animations. Frame animation: is the easiest kind of anima ...

Property name describe prototype Adding attributes and methods to objects constructor Returns an array object reference length Returns the number of array elements Method name describe Return Change the original array concat() Connect multiple arrays New array after connection N join('') Combines all elements in an array into ...