Python error:
attributeerror: ‘nonetype’ object has no attribute ‘append’

a=[]
b=[1,2,3,4]
a = a.append(b)

After one execution, the type of a changes to nonetype
the above errors will appear in the next execution.

This is because append modifies a itself and returns none. The return value cannot be reassigned to a.

terms of settlement:

Change the variable name:
C =]
b = [1,2,3,4]
C = A. append (b)
problem solving.

Or
change a = a.append (b) to a.append (b)

npm ERR! code 1
npm ERR! path /Users/tangwenjing/Html/imooc/my-app1/node_modules/canvas
npm ERR! command failed
npm ERR! command sh -c node-gyp rebuild
npm ERR! /bin/sh: pkg-config: command not found
npm ERR! gyp: Call to 'pkg-config pixman-1 --libs' returned exit status 127 while in binding.gyp. while trying to load binding.gyp
npm ERR! gyp ERR! configure error 
npm ERR! gyp ERR! stack Error: `gyp` failed with exit code: 1
npm ERR! gyp ERR! stack     at ChildProcess.onCpExit (/Users/tangwenjing/Html/imooc/my-app1/node_modules/node-gyp/lib/configure.js:351:16)
npm ERR! gyp ERR! stack     at ChildProcess.emit (events.js:376:20)
npm ERR! gyp ERR! stack     at Process.ChildProcess._handle.onexit (internal/child_process.js:277:12)
npm ERR! gyp ERR! System Darwin 20.4.0
npm ERR! gyp ERR! command "/usr/local/bin/node" "/Users/tangwenjing/Html/imooc/my-app1/node_modules/.bin/node-gyp" "rebuild"
npm ERR! gyp ERR! cwd /Users/tangwenjing/Html/imooc/my-app1/node_modules/canvas
npm ERR! gyp ERR! node -v v14.17.0
npm ERR! gyp ERR! node-gyp -v v7.1.2
npm ERR! gyp ERR! not ok

npm ERR! A complete log of this run can be found in:
npm ERR!     /Users/tangwenjing/.npm/_logs/2021-06-03T09_55_42_223Z-debug.log

Solution: install nodejs installation package directly because of the NPM version problem

sudo apt install libssl-dev

Do is a post function, post can be displayed after the details, the error is in the post after clicking the error
first of all, the meaning of the question is that the “title” attribute cannot be found in the list class, which means that the data is queried, but the title attribute cannot be found
after re checking one side of the code, it is found that there is no problem, that is, the method return type of the POJO class in the Dao layer is not written correctly. I wrote the list type at that time, but all I want to display is a message. List is a collection type, which can’t be found. Therefore, you can change the list type to the entity type consult.

@echo off
cd %windir%\system32\
start notepad.exe C:\Windows\System32\drivers\etc\hosts

Create a new folder and change the extension name to bat

 mhpt>nginx -s reload
nginx: [error] OpenEvent("Global\ngx_reload_11812") failed (2: The system cannot find the file specified)

  This is because nginx is not started, so an error is reported when reloading.

Tab case

First, CSS style

* {
      margin: 0;
      padding: 0;
    }

    .tab ul {
      overflow: hidden;
      padding: 0;
      margin: 0;
    }

    .tab ul li {
      box-sizing: border-box;
      padding: 0;
      float: left;
      width: 100px;
      height: 45px;
      line-height: 45px;
      list-style: none;
      text-align: center;
      border-top: 1px solid blue;
      border-right: 1px solid blue;
      cursor: default
    }

    .tab ul li:first-child {
      border-left: 1px solid blue;
    }

    .tab ul li.active {
      background-color: orange;
    }

    .tab div {
      width: 500px;
      height: 300px;
      display: none;
      text-align: center;
      font-size: 30px;
      line-height: 300px;
      border: 1px solid blue;
      border-top: 0px;
    }

    .tab div.current {
      display: block;
    }

Second, structure

<div id="app">
    <div class="tab">
      <ul>
        <li class="active">apple</li>
        <li>orange</li>
        <li>lemon</li>
      </ul>
      <div class="current">
        <img src="img/apple.png">
      </div>
      <div>
        <img src="img/orange.png">
      </div>
      <div>
        <img src="img/lemon.png">
      </div>
    </div>
  </div>

Third: JS logic

var vm = new Vue({
      el: '#app',
      data: {
      }，
    methods: {
     }
)}

The following is the result of the HTML structure and JS code

1. HTML structure

<div id="app">
    <div class="tab">
      <!--  tab  -->
      <ul>
        <!-- dynamically bound class with active class name highlighted without active not highlighted-->
        <li @click="change(index)" :class='currentIndex==index?"active":""' v-for="(item, index) in list"
          :key="item.id">
          {{item.title}}</li>
      </ul>
      <!--  Corresponding displayed images -->
      <! -- dynamically bound class with current class name shown without current hidden-->
      <div :class="currentIndex==index?'current':''" v-for="(item, index) in list" :key="item.id"><img :src="item.path">
      </div>
    </div>
  </div>

2. JS logic

let vm = new Vue({
      el: '#app',
      data: {
        currentIndex: 0,// The current index of the tab defaults to 0  
        list: [{
          id: 1,
          title: 'apple',
          path: 'img/apple.png'
        },
        {
          id: 2,
          title: 'orange',
          path: 'img/orange.png'
        },
        {
          id: 3,
          title: 'lemon',
          path: 'img/lemon.png'
        }]
      },
      methods: {
        // The currentIndex is equal to the clicked index value by passing in the index 
        // thus controlling the class name    
        change(index) {
          this.currentIndex = index
        }
      }
    })

Tab view

example:

package main

import (
    "fmt"
    "io/ioutil"
)

func main() {
    dirname := "/root/test"
    dir, _ := ioutil.ReadDir(dirname)
    if len(dir) == 0 {
        fmt.Println(dirname + " is empty dir!")
    } else {
        fmt.Println(dirname + " is not empty dir!")
    }
}