Programmer Think

introduction Yesterday, I finished process control and talked about some of the simplest built-in methods of basic data types. Let's continue with the built-in method today. There are many built-in methods. Don't be afraid. As long as you use more, you will be able to write it when you think of it. String built-in method Remove leading and tr ...

Two dimensional data, Series container, with both row index and column index     1. Create DataFrame 1.1 create DataFrame through list You need to specify data, index row and columns Specify that data and index/columns are of type list or NP arange df1 = pd.DataFrame(data=[[1, 2, 3], [11, 12, 13]], index=['r_1', 'r_2'], colum ...

Shift operators Shift right The right shift is divided into: Arithmetic shift: discard the right and fill the original symbol bit on the left Shift left: 0, fill right: 0 Positive shift method A binary number contains the inverse complement of the original code When shifting, the complement is moved Positive number For example: int a ...

Transaction What is a transaction? A smallest non separable work unit; Usually, a transaction corresponds to a complete business (for example, bank account transfer business, which is the smallest work unit) A complete business requires batch DML(insert, update, delete) statements to be jointly completed Transactions are only related ...

preface Webpack is a very powerful front-end resource loading / packaging tool. It can perform static analysis according to the dependencies of modules, and then generate static resources according to certain rules (the following contents are regulated in webpack 5) Official website 1, webpack installation 1. Initialize npm npm init ...

1, Basic overview 1.1 what is spring? ​ Spring is a lightweight java development framework rising in 2003. It is created to solve the complexity of enterprise application development. The core of spring is inversion of control (IoC) and aspect oriented programming (AOP). Spring is a lightweight open source framework that can be used in Java ...

Basic Java learning - Chapter 3 array 1, Overview of arrays 1. Definition of array An Array is a collection of multiple data of the same type arranged in a certain order, named with a name, and managed uniformly by numbering. 2. Array related concepts Array nameSubscript (index)elementLength of the array (number of elements) 3. Characteri ...

I Set up SSH service 1. Turn off the firewall and SELinux 2. Configure yum source 3. Installation of openssh software The underlying software name of SSH service is openssh. open source, SSH is SSH service. Openssh belongs to C/S architecture software, which has client and server. Client: ssh Server: openssh server Installation steps ...

There is a classic question in Web Development: "what happens in the browser from entering URL to page rendering?"According to my research, this problem has a history of at least ten years. In the ever-changing front-end circle, this question can be asked all the time because it is a very good question, involving a lot of knowledge po ...

1, Overview of collection framework 1. Sets and arrays are structures that store multiple data, referred to as Java containers for short    note: storage at this time mainly refers to memory storage, and does not involve persistent storage (. txt,.jpg,.avi, database) 2. Characteristics of array in storing multiple data:  &emsp ...