57个挑战（pythonjava）lesson42（2）

　　在昨天题目基础上做挑战问题：
　　在金额上增加一个$符号 和逗号。- 这个在展示函数上直接增加即可。以金额高低来做排序。重写程序，主要用csv 的解析库来实现解析效果。
　　挑战2两个求解思路，
　　方法1 ： 建设2个字典，以Salary 为 key， 以First 和 Last 为value。 这样做排序的时候，先对Salary list 做排序， 然后基于这两个字典做查询即可。
　　方法2: 把Salary 的 list 中的元素index 单独抽出来，在做排序的时候，记录原始index的最后位置，再根据这个位置在list 里寻找数据。--这个之前挑战已经做过了，有demo。
　　方法3: 把这些内容存到数据库里，做一条查询即可，再做展示。
　　挑战3的代码如下：
　　python 版本：import csv class Parsedatafile:     originallist = []     firstcolumn = []     seconcolumn = []     thirdcolumn = []      def readdatafile(this):         # 从指定的文件中读取数据，并读入到一个列表中         filename = input(＂Please provde the name of the file from which you want open＂)         with open(filename, ＂r＂) as f:             reader = csv.reader(f)             for line in reader:                 this.originallist.append(line)             f.close()         print(＂this is the list we get from the file {0}＂.format(this.originallist))      def processlist(this):         # 对列表做格式化，并生成对应的三个队列         for i in this.originallist:             this.firstcolumn.append(i[0])             this.seconcolumn.append(i[1])             this.thirdcolumn.append(i[2])          print(＂This is the firstcolumn list: {0}＂.format(this.firstcolumn))         print(＂This is the secondcolumn list: {0}＂.format(this.seconcolumn))         print(＂This is the thirdcolumn list: {0}＂.format(this.thirdcolumn))      def displaylist(this):         # 对处理后的队列操作，逐行做展示         # 找到每个列表里面最宽的元素         col1length = 0         col2length = 0         col3length = 0         for i in this.firstcolumn:             if len(i) > col1length:                 col1length = len(i)         for i in this.seconcolumn:             if len(i) > col2length:                 col2length = len(i)         for i in this.thirdcolumn:             if len(i) > col3length:                 col3length = len(i)         space = ＂ ＂         line1 = ＂Last＂ + space * (col1length - 4 + 1) + ＂First＂ + space * (col2length - 5 + 1) + ＂Salary＂ + space * (                     col3length - 6 + 1)         line2 = len(line1) * ＂-＂         print(line1)         print(line2)         for i in range(0, len(this.firstcolumn)):             print(this.firstcolumn[i].ljust(col1length + 1), end=＂＂)             print(this.seconcolumn[i].ljust(col2length + 1), end=＂＂)             print(this.thirdcolumn[i])   lesson42 = Parsedatafile() lesson42.readdatafile() lesson42.processlist() lesson42.displaylist()
　　python csv 函数的详细用法可以参考网文，
　　https://blog.csdn.net/xietansheng/article/details/117604917
　　这里主要是把每一行的数据解析成了一个队列。
　　看到下面运行效果是一样的。
　　Java 版本：
　　使用csvReader来解析CSV 文件，效果类似，也是解析成了一个队列，从队列里面直接读取元素即可。
　　import java.io.BufferedReader; import java.io.FileReader; import java.io.IOException; import java.io.InputStreamReader; import java.nio.Buffer; import java.util.ArrayList; import java.util.Scanner; import com.opencsv.CSVReader;  public class ParseFilev2{     private ArrayList  originallist = new ArrayList<>();     private ArrayList  firstcolumn = new ArrayList<>();     private ArrayList  secondcolumn = new ArrayList<>();     private ArrayList  thirdcolumn = new ArrayList<>();     private Scanner sc = new Scanner(System.in);      void readdatafile(){         System.out.println(＂Please provde the name of the file from which you want open＂);         String filename = sc.nextLine();         try{             String[] nextLine;             CSVReader csvReader = new CSVReader(new FileReader(filename));             while((nextLine=csvReader.readNext())!= null)             {                 firstcolumn.add(nextLine[0]);                 secondcolumn.add(nextLine[1]);                 thirdcolumn.add(nextLine[2]);                 originallist.add(nextLine[0]+＂,＂+nextLine[1]+＂,＂+nextLine[2]);             }         }catch(IOException e){          }         System.out.println(＂This is the original list we get from the file＂+ originallist.toString());     }     //从指定的文件中读取数据，并读入到一个列表中        void displaylist(){         //对处理后的队列操作，逐行做展示         //找到每个列表里面最宽的元素         int fcmlength = 0;         int scmlength = 0;         int tcmlength = 0;         for (int i = 0 ; i< firstcolumn.size();i++){             if (fcmlength< firstcolumn.get(i).length())             {fcmlength = firstcolumn.get(i).length();}             if (scmlength< secondcolumn.get(i).length())             {scmlength = secondcolumn.get(i).length();}             if (tcmlength< thirdcolumn.get(i).length())             {tcmlength = thirdcolumn.get(i).length();}         }         fcmlength = fcmlength + 1;         scmlength = scmlength + 1;         tcmlength = tcmlength + 1;         System.out.printf(＂%-＂+fcmlength+＂s＂,＂Last＂);         System.out.printf(＂%-＂+scmlength+＂s＂,＂First＂);         System.out.printf(＂%-＂+tcmlength+＂s ＂,＂Salary＂);         for(int j=0;j< fcmlength+scmlength+tcmlength;j++)         {             System.out.printf(＂-＂);         }         System.out.println();          for( int k =0 ;k < firstcolumn.size();k++)         {             System.out.printf(＂%-＂+fcmlength+＂s＂, firstcolumn.get(k));             System.out.printf(＂%-＂+scmlength+＂s＂, secondcolumn.get(k));             System.out.printf(＂%-＂+tcmlength+＂s＂, thirdcolumn.get(k));             System.out.println();         }         }      public static void main(String[] args)     {         ParseFilev2 lesson42 = new ParseFilev2();         lesson42.readdatafile();         lesson42.displaylist();     } }
　　效果图：