filereader | 易学教程

fileReader.readAsBinaryString to upload files

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问题 Trying to use fileReader.readAsBinaryString to upload a PNG file to the server via AJAX, stripped down code (fileObject is the object containing info on my file); var fileReader = new FileReader(); fileReader.onload = function(e) { var xmlHttpRequest = new XMLHttpRequest(); //Some AJAX-y stuff - callbacks, handlers etc. xmlHttpRequest.open("POST", '/pushfile', true); var dashes = '--'; var boundary = 'aperturephotoupload'; var crlf = "\r\n"; //Post with the correct MIME type (If the OS can

Change specific value in CSV file via Python

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问题 I need the way to change specific value of the column of csv file. For example I have csv file: "Ip","Sites" "127.0.0.1",10 "127.0.0.2",23 "127.0.0.3",50 and I need to change value 23 to 30 of the "127.0.0.2". I use csv library: import csv Appreciate any help as I'm new in Python. Thanks! 回答1: This is the solution opening the csv file, changing the values in memory and then writing back the changes to disk. r = csv.reader(open('/tmp/test.csv')) # Here your csv file lines = list(r) Content of

【前端知乎系列】ArrayBuffer 和 Blob 对象

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【推荐】2019 Java 开发者跳槽指南.pdf(吐血整理) >>> 本文首发在我的【个人博客】更多丰富的前端学习资料，可以查看我的 Github : 《Leo-JavaScript》，内容涵盖数据结构与算法、 HTTP 、 Hybrid 、面试题、 React 、 Angular 、 TypeScript 和 Webpack 等等。点个 Star 不迷路~ ArrayBuffer 对象与 Blob 对象大家或许不太陌生，常见于文件上传操作处理（如处理图片上传预览等问题）。那么本文将与大家深入介绍两者。一、ArrayBuffer 对象 ArrayBuffer 对象是 ES6 才纳入正式 ECMAScript 规范，是 JavaScript 操作二进制数据的一个接口。 ArrayBuffer 对象是以数组的语法处理二进制数据，也称二进制数组。介绍 ArrayBuffer 对象还需介绍 TypedArray 视图和 DataView 视图，本文不具体介绍，详细可以查看阮一峰老师《ECMAScript 6 入门 ArrayBuffer》章节。 1. 概念介绍 ArrayBuffer 对象代表储存二进制数据的一段内存，它不能直接读写，只能通过视图（ TypedArray 视图和 DataView 视图）来读写，视图的作用是以指定格式解读二进制数据。关于

java IO流三：字符流 FileReader & FileWriter

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FileReader package com . company01 . IO ; /* java.io.Reader; java.InputStreamReader; 转换流（字节输入流 ---> 字符输入流） java.io.FileReader; 文件字符输入流只能读取纯文本，字符流可以一次读取一个汉字，而字节流只能读取汉字的一半，字节流容易出现乱码 */ import java . io . * ; public class FileReadrTest01 { public static void main ( String [ ] args ) { FileReader fr = null ; try { fr = new FileReader ( "test01" ) ; // 开始读 char [ ] chars = new char [ 215 ] ; // 1KB int temp = 0 ; while ( ( temp = fr . read ( chars ) ) != - 1 ) { // 将char数组有效部分转换成字符串 System . out . print ( new String ( chars , 0 , temp ) ) ; } } catch ( Exception e ) { e . printStackTrace ( ) ; }

Skipping in my File Reader

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问题 public void file(){ String fileName = "hello.txt"; fileName = FileBrowser.chooseFile(true); //Open a file and store the information into the OurList try { String s = ""; File file = new File(fileName); FileReader inputFile = new FileReader(file); while( inputFile.read() != -1) { System.out.println(inputFile.read()); System.out.println(); } } catch(Exception exception) { System.out.println("Not a real file. List is already built"); } } So i am having trouble with this piece of code. I want to

canvas和base64

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base64是二进制数据的一个编码格式，就像utf8一样的东西他跟json一样，也是前后端交互能够相互识别的数据，他更多的是用来传递文件数据在js里生成base64的API有两个，一个是 FileReader ，一个是画布 canvas FileReader <input type="file" onchange="change(this.files[0])"> function change(file){ var fr = new FileReader() fr.onload = function(e) { // 这个就是base64 console.log( e.target.result ); } // 这个方法传参是一个Blob类型的格式 fr.readAsDataURL(file) } canvas 我们使用画布是为了获取画布上的内容画布的输入是图片，然后对这个图片进行剪切，打水印什么的画布上的内容的输出格式是base64 // 这个image就是输入 // 除了new，也可以直接取页面上的标签 var image = new Image(); image.onload = function () { var w = image.width; var h = image.height; var canvas = document.createElement(

how to read json object in python [duplicate]

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问题 This question already has answers here : can't read json file with python. getting type error: json object is 'TextIOWrapper' (3 answers) Closed last year . i have json file named "panamaleaks50k.json" . I want to get ['text'] field from json file but it shows me following error the JSON object must be str, bytes or bytearray, not 'TextIOWrapper' this is my code with open('C:/Users/bilal butt/Desktop/PanamalEakJson.json','r') as lst: b = json.loads(lst) print(b['text']) my json file look [ {

FileReader class in C#

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问题 I am looking for fast class for to work with text files and comfortable reading different object (methods like NextInt32, NextDouble, NextLine, etc). Can you advice me something? Edit: BinaryReader is bad class in my case. Format of my data is not binary. I have file like 1 2 3 FirstToken NextToken 1.23 2,34 And I want read this file with code like: int a = FileReader.NextInt32(); int b = FileReader.NextInt32(); int c = FileReader.NextInt32(); int d = FileReader.NextString(); int e =

2017.12.31 JS拖拽本地图片显示

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HTML部分 <div id="img1" class="box1" ondragover="dragOver(event)" ondrop="picture(event)"></div> <div id="img2" class="box2" ondragover="dragOver(event)" ondrop="picture(event)"></div> <div id="img3" class="box3" ondragover="dragOver(event)" ondrop="picture(event)"></div> <div id="img4" class="box4" ondragover="dragOver(event)" ondrop="picture(event)"></div> CSS样式部分 div{width: auto;height: 400px;} .box1{background-color: lightblue} .box2{background-color: lightcoral} .box3{background-color: lightcyan} .box4{background-color: lightgoldenrodyellow} JS部分 function dragStart(e) { e.dataTransfer

How to read multiple lines using FileReader only?

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问题 I have the following code: public class Reader { public static void main(String[] args) throws IOException { try (FileReader in = new FileReader("D:/test.txt")) { // BufferedReader br = new BufferedReader(in); int line = in .read(); for (int i = 0; i < line; i++) { //System.out.println(line); System.out.println((char) line); line = in .read(); } } } } and a file Test.txt with the content: Hello Java When I run above code it only reads Hello . I would like to read multiple lines using