csv导出后有省略号

CSV文件在保存长文本或者数值时，如果内容超过单元格的宽度限制，通常会自动显示省略号（...）来表示部分内容被截断了。这主要是因为CSV默认采用固定的列宽，并非像Excel那样能自适应调整。如果你在Python中使用`csv`模块导出时遇到这种情况，可能是由于列宽设置不足导致的。

解决这个问题主要有以下几种方法：

1. **增加列宽**：如果你有控制列宽的能力，可以在创建CSV文件时指定更大的宽度。例如，可以设置`field_size_limit`参数来提高最大字段长度（仅对Python 3.7+有效）：

import csv
with open('output.csv', 'w', newline='', field_size_limit=10000)  # 更大的列宽限制

2. **调整输出格式**：在输出时，你可以选择不保留多余的字符，而是直接切片到某个特定长度。但是这可能会丢失信息，取决于你选择的截断策略。

3. **程序中处理**：在生成CSV之前，先检查内容是否过长，然后适当处理。例如，对于文本内容，可以考虑分段或者使用HTML实体替换省略号。

4. **使用其他工具**：如果列内容确实很长，可能需要考虑使用专门的数据可视化库，如`pandas`的`.to_string()`或`.to_csv`函数，它们提供了更多的控制选项。

相关问题

4)车票管理系统 一车站每天有n个发车班次，每个班次都有一班此号（1,2,3，....n）,固定的发车时间，固定的路线（起始站，终点站），大致的行车时间，固定的额定载客量。 （1）班次信息的增删改查，支持导入班次信息（格式自定义） （2）浏览班次信息可显示所有班次当前状况，如果当前系时间超过了耨班次的发车时间，则显示“此班已发出”的提示信息。 （3）查询路线：可按班次号查询，可按终点站查询 （4）统计售票情况 （5）售票和退票功能 （6）支持用户导出购票情况设计环境为Windows+Eclipse+JDK+Tomcat+MySQL用代码实现

以下是一个简单的示例代码，使用了Java语言和MySQL数据库：

1. 数据库设计

CREATE TABLE `ticket` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `train_number` varchar(20) NOT NULL,
  `start_station` varchar(50) NOT NULL,
  `end_station` varchar(50) NOT NULL,
  `departure_time` datetime NOT NULL,
  `estimated_time` int(11) NOT NULL,
  `capacity` int(11) NOT NULL,
  `sold_tickets` int(11) NOT NULL DEFAULT '0',
  PRIMARY KEY (`id`)
);

2. 后端Java代码

Ticket.java

public class Ticket {
    private int id;
    private String trainNumber;
    private String startStation;
    private String endStation;
    private Date departureTime;
    private int estimatedTime;
    private int capacity;
    private int soldTickets;

    // 构造函数、getter和setter方法省略
}

TicketDAO.java

public class TicketDAO {
    private Connection conn;

    public TicketDAO() {
        try {
            Class.forName("com.mysql.jdbc.Driver");
            String url = "jdbc:mysql://localhost:3306/ticket_management";
            String user = "root";
            String password = "root";
            conn = DriverManager.getConnection(url, user, password);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public List<Ticket> getAllTickets() {
        List<Ticket> tickets = new ArrayList<Ticket>();
        try {
            Statement stmt = conn.createStatement();
            ResultSet rs = stmt.executeQuery("SELECT * FROM ticket");
            while (rs.next()) {
                Ticket ticket = new Ticket();
                ticket.setId(rs.getInt("id"));
                ticket.setTrainNumber(rs.getString("train_number"));
                ticket.setStartStation(rs.getString("start_station"));
                ticket.setEndStation(rs.getString("end_station"));
                ticket.setDepartureTime(rs.getDate("departure_time"));
                ticket.setEstimatedTime(rs.getInt("estimated_time"));
                ticket.setCapacity(rs.getInt("capacity"));
                ticket.setSoldTickets(rs.getInt("sold_tickets"));
                tickets.add(ticket);
            }
            rs.close();
            stmt.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return tickets;
    }

    public List<Ticket> getTicketsByTrainNumber(String trainNumber) {
        List<Ticket> tickets = new ArrayList<Ticket>();
        try {
            PreparedStatement stmt = conn.prepareStatement("SELECT * FROM ticket WHERE train_number = ?");
            stmt.setString(1, trainNumber);
            ResultSet rs = stmt.executeQuery();
            while (rs.next()) {
                Ticket ticket = new Ticket();
                ticket.setId(rs.getInt("id"));
                ticket.setTrainNumber(rs.getString("train_number"));
                ticket.setStartStation(rs.getString("start_station"));
                ticket.setEndStation(rs.getString("end_station"));
                ticket.setDepartureTime(rs.getDate("departure_time"));
                ticket.setEstimatedTime(rs.getInt("estimated_time"));
                ticket.setCapacity(rs.getInt("capacity"));
                ticket.setSoldTickets(rs.getInt("sold_tickets"));
                tickets.add(ticket);
            }
            rs.close();
            stmt.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return tickets;
    }

    public List<Ticket> getTicketsByEndStation(String endStation) {
        List<Ticket> tickets = new ArrayList<Ticket>();
        try {
            PreparedStatement stmt = conn.prepareStatement("SELECT * FROM ticket WHERE end_station = ?");
            stmt.setString(1, endStation);
            ResultSet rs = stmt.executeQuery();
            while (rs.next()) {
                Ticket ticket = new Ticket();
                ticket.setId(rs.getInt("id"));
                ticket.setTrainNumber(rs.getString("train_number"));
                ticket.setStartStation(rs.getString("start_station"));
                ticket.setEndStation(rs.getString("end_station"));
                ticket.setDepartureTime(rs.getDate("departure_time"));
                ticket.setEstimatedTime(rs.getInt("estimated_time"));
                ticket.setCapacity(rs.getInt("capacity"));
                ticket.setSoldTickets(rs.getInt("sold_tickets"));
                tickets.add(ticket);
            }
            rs.close();
            stmt.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return tickets;
    }

    public void addTicket(Ticket ticket) {
        try {
            PreparedStatement stmt = conn.prepareStatement("INSERT INTO ticket (train_number, start_station, end_station, departure_time, estimated_time, capacity, sold_tickets) VALUES (?, ?, ?, ?, ?, ?, ?)");
            stmt.setString(1, ticket.getTrainNumber());
            stmt.setString(2, ticket.getStartStation());
            stmt.setString(3, ticket.getEndStation());
            stmt.setDate(4, new java.sql.Date(ticket.getDepartureTime().getTime()));
            stmt.setInt(5, ticket.getEstimatedTime());
            stmt.setInt(6, ticket.getCapacity());
            stmt.setInt(7, ticket.getSoldTickets());
            stmt.executeUpdate();
            stmt.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public void updateTicket(Ticket ticket) {
        try {
            PreparedStatement stmt = conn.prepareStatement("UPDATE ticket SET train_number = ?, start_station = ?, end_station = ?, departure_time = ?, estimated_time = ?, capacity = ?, sold_tickets = ? WHERE id = ?");
            stmt.setString(1, ticket.getTrainNumber());
            stmt.setString(2, ticket.getStartStation());
            stmt.setString(3, ticket.getEndStation());
            stmt.setDate(4, new java.sql.Date(ticket.getDepartureTime().getTime()));
            stmt.setInt(5, ticket.getEstimatedTime());
            stmt.setInt(6, ticket.getCapacity());
            stmt.setInt(7, ticket.getSoldTickets());
            stmt.setInt(8, ticket.getId());
            stmt.executeUpdate();
            stmt.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public void deleteTicket(int id) {
        try {
            PreparedStatement stmt = conn.prepareStatement("DELETE FROM ticket WHERE id = ?");
            stmt.setInt(1, id);
            stmt.executeUpdate();
            stmt.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public void sellTicket(int id) {
        try {
            PreparedStatement stmt = conn.prepareStatement("UPDATE ticket SET sold_tickets = sold_tickets + 1 WHERE id = ?");
            stmt.setInt(1, id);
            stmt.executeUpdate();
            stmt.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public void refundTicket(int id) {
        try {
            PreparedStatement stmt = conn.prepareStatement("UPDATE ticket SET sold_tickets = sold_tickets - 1 WHERE id = ?");
            stmt.setInt(1, id);
            stmt.executeUpdate();
            stmt.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public void exportTicketSales() {
        try {
            Statement stmt = conn.createStatement();
            ResultSet rs = stmt.executeQuery("SELECT * FROM ticket");
            FileWriter writer = new FileWriter("ticket_sales.csv");
            writer.append("id,train_number,start_station,end_station,departure_time,estimated_time,capacity,sold_tickets\n");
            while (rs.next()) {
                writer.append(String.valueOf(rs.getInt("id")));
                writer.append(",");
                writer.append(rs.getString("train_number"));
                writer.append(",");
                writer.append(rs.getString("start_station"));
                writer.append(",");
                writer.append(rs.getString("end_station"));
                writer.append(",");
                writer.append(rs.getDate("departure_time").toString());
                writer.append(",");
                writer.append(String.valueOf(rs.getInt("estimated_time")));
                writer.append(",");
                writer.append(String.valueOf(rs.getInt("capacity")));
                writer.append(",");
                writer.append(String.valueOf(rs.getInt("sold_tickets")));
                writer.append("\n");
            }
            writer.flush();
            writer.close();
            rs.close();
            stmt.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

TicketController.java

public class TicketController extends HttpServlet {
    private TicketDAO ticketDAO;

    public void init() {
        ticketDAO = new TicketDAO();
    }

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String action = request.getParameter("action");
        if (action == null) {
            action = "list";
        }
        switch (action) {
            case "list":
                listTickets(request, response);
                break;
            case "add":
                addTicket(request, response);
                break;
            case "edit":
                editTicket(request, response);
                break;
            case "update":
                updateTicket(request, response);
                break;
            case "delete":
                deleteTicket(request, response);
                break;
            case "sell":
                sellTicket(request, response);
                break;
            case "refund":
                refundTicket(request, response);
                break;
            case "export":
                exportTicketSales(request, response);
                break;
            default:
                listTickets(request, response);
                break;
        }
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

    private void listTickets(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        List<Ticket> tickets = ticketDAO.getAllTickets();
        request.setAttribute("tickets", tickets);
        request.getRequestDispatcher("list_tickets.jsp").forward(request, response);
    }

    private void addTicket(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        Ticket ticket = new Ticket();
        ticket.setTrainNumber(request.getParameter("train_number"));
        ticket.setStartStation(request.getParameter("start_station"));
        ticket.setEndStation(request.getParameter("end_station"));
        try {
            SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
            Date departureTime = dateFormat.parse(request.getParameter("departure_time"));
            ticket.setDepartureTime(departureTime);
        } catch (Exception e) {
            e.printStackTrace();
        }
        ticket.setEstimatedTime(Integer.parseInt(request.getParameter("estimated_time")));
        ticket.setCapacity(Integer.parseInt(request.getParameter("capacity")));
        ticket.setSoldTickets(Integer.parseInt(request.getParameter("sold_tickets")));
        ticketDAO.addTicket(ticket);
        response.sendRedirect("ticket?action=list");
    }

    private void editTicket(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        int id = Integer.parseInt(request.getParameter("id"));
        Ticket ticket = ticketDAO.getTicketById(id);
        request.setAttribute("ticket", ticket);
        request.getRequestDispatcher("edit_ticket.jsp").forward(request, response);
    }

    private void updateTicket(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        Ticket ticket = new Ticket();
        ticket.setId(Integer.parseInt(request.getParameter("id")));
        ticket.setTrainNumber(request.getParameter("train_number"));
        ticket.setStartStation(request.getParameter("start_station"));
        ticket.setEndStation(request.getParameter("end_station"));
        try {
            SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm