cpp: read csv file

 

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// CSVfilemanagement.h : //练习案例：CSV 文件读写 // // 2023年4月5日 涂聚文 Geovin Du edit. // https://www.digitalocean.com/community/tutorials/getline-in-c-plus-plus // https://www.geeksforgeeks.org/csv-file-management-using-c/ // https://codereview.stackexchange.com/questions/211826/code-to-read-and-write-csv-files // https://thispointer.com/how-to-read-data-from-a-csv-file-in-c/ // https://github.com/vincentlaucsb/csv-parser //https://codereview.stackexchange.com/questions/211826/code-to-read-and-write-csv-files //https://www.geeksforgeeks.org/csv-file-management-using-c/ //https://github.com/awdeorio/csvstream //https://cplusplus.com/forum/general/282647/ //https://cplusplus.com/forum/beginner/221913/ //https://www.example-code.com/cpp/csv_update.asp //https://www.chilkatsoft.com/dotnet-core.asp //https://www.codeproject.com/articles/741183/cplusplus-minimalistic-csv-streams#history //https://github.com/iamantony/qtcsv // //https://sourceforge.net/projects/cccsvparser/ //https://github.com/ben-strasser/fast-cpp-csv-parser //https://www.codeproject.com/articles/741183/cplusplus-minimalistic-csv-streams //https://en.cppreference.com/w/cpp/header/filesystem // // // // // // // // // //       #pragma once #ifndef CSVFILEMANAGEMENT_H #define CSVFILEMANAGEMENT_H     #include <iostream> #include <string> #include <vector> #include <memory>  #include <string>       /**  * @brief  * \author geovindu.  * \date 20230-4-10  */ namespace geovindu {     /**      * @brief CSV 文件操作      * .      */     class CSVfilemanagement     {         private:                   public:             /// <summary>         ///         ///         /// </summary>         /// <param name="s"></param>         /// <returns></returns>         //string ReverseString(string& s);         /// <summary>         ///         /// </summary>         /// <param name="path"></param>         /// <returns></returns>         //string readFileIntoDuString(string path);         /// <summary>         ///         /// </summary>         /// <param name="path"></param>         /// <returns></returns>         //string readTextFileIntoString(const string& path);         /// <summary>         ///         /// </summary>            void getReadFile();         /// <summary>         ///         /// </summary>         /// <param name="filename"></param>         /// <param name="dataset"></param>         void write_csv(std::string filename, std::vector<std::pair<std::string, std::vector<int>>> dataset);           std::vector<std::pair<std::string, std::vector<int>>> read_csv(std::string filename);         /// <summary>         ///         /// </summary>         /// <param name="line_data"></param>         void DisplayRowCsv(std::vector<std::string> line_data);         /**          * @brief 写.          *          */         void create();         /**          * @brief 读.          *          */         void read_record();         /// <summary>         /// 读取全部记录         /// </summary>         void readAll();           /**          * @brief 更新.          *          */         void update_recode();         /**          * @brief 删除.          *          */         void delete_record();       };   }   #endif

　　

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// CSVfilemanagement.cpp : //练习案例：CSV 文件读写 // // 2023年4月5日 涂聚文 Geovin Du edit. // //     #include "CSVfilemanagement.h"     #include <memory>  #include <string>    // std::string #include <fstream>   // std::ofstream, std::ifstream #include <vector>    // std::vector #include <utility>   // std::pair #include <stdexcept> // std::runtime_error #include <sstream>   // std::stringstream #include <iostream>  // std::cout, std::cin #include <map> #include <algorithm> #include <iterator>     //#include <bits/stdc++.h>   using std::cout; using std::endl; using std::string; using std::reverse;     using namespace std;   /**  * @brief  * \author geovindu.  * \date 20230-4-10  */ namespace geovindu {         /// <summary>     ///     /// </summary>     /// <param name="s"></param>     /// <returns></returns>     string ReverseString(string& s) {        string rev(s.rbegin(), s.rend());         return rev;     }     /// <summary>     /// text file     /// </summary>     /// <param name="path"></param>     /// <returns></returns>     string readTextFileIntoString(string path) {         ifstream input_file(path);         if (!input_file.is_open()) {             cerr << "Could not open the file - '"                 << path << "'" << endl;             exit(EXIT_FAILURE);         }         return string((std::istreambuf_iterator<char>(input_file)), std::istreambuf_iterator<char>());     }     /// <summary>     /// csv file     /// </summary>     /// <param name="path"></param>     /// <returns></returns>     string readFileIntoDuString(string path) {         auto ss = ostringstream{};         ifstream input_file(path);         if (!input_file.is_open()) {             cerr << "Could not open the file - '"                 << path << "'" << endl;             exit(EXIT_FAILURE);         }         ss << input_file.rdbuf();         return ss.str();     }       /// <summary>     ///     /// </summary>     /// <param name="file"></param>     void CSVfilemanagement::getReadFile()     {         string filename("reportcard.csv"); //"grades.csv"         string file_contents;         std::map<int, std::vector<string>> csv_contents;         char delimiter = ',';           file_contents = readFileIntoDuString(filename);           istringstream sstream(file_contents);         std::vector<string> items;         string record;           int counter = 0;         while (std::getline(sstream, record)) {             istringstream line(record);             while (std::getline(line, record, delimiter)) {                 items.push_back(record);                // std::cout << record << std::endl;             }               csv_contents[counter] = items;             std::cout << csv_contents[counter].size() << std::endl;             items.clear();             counter += 1;         }     }     /// <summary>     ///     /// </summary>     /// <param name="filename"></param>     /// <param name="dataset"></param>     void CSVfilemanagement::write_csv(std::string filename, std::vector<std::pair<std::string, std::vector<int>>> dataset) {         // Make a CSV file with one or more columns of integer values         // Each column of data is represented by the pair <column name, column data>         //   as std::pair<std::string, std::vector<int>>         // The dataset is represented as a vector of these columns         // Note that all columns should be the same size           // Create an output filestream object         std::ofstream myFile(filename);           // Send column names to the stream         for (int j = 0; j < dataset.size(); ++j)         {             myFile << dataset.at(j).first;             if (j != dataset.size() - 1) myFile << ","; // No comma at end of line         }         myFile << "\n";           // Send data to the stream         for (int i = 0; i < dataset.at(0).second.size(); ++i)         {             for (int j = 0; j < dataset.size(); ++j)             {                 myFile << dataset.at(j).second.at(i);                 if (j != dataset.size() - 1) myFile << ","; // No comma at end of line             }             myFile << "\n";         }           // Close the file         myFile.close();     }     /// <summary>     ///     /// </summary>     /// <param name="filename"></param>     /// <returns></returns>     std::vector<std::pair<std::string, std::vector<int>>> CSVfilemanagement::read_csv(std::string filename) {         // Reads a CSV file into a vector of <string, vector<int>> pairs where         // each pair represents <column name, column values>           // Create a vector of <string, int vector> pairs to store the result         std::vector<std::pair<std::string, std::vector<int>>> result;           // Create an input filestream         std::ifstream myFile(filename);           // Make sure the file is open         if (!myFile.is_open()) throw std::runtime_error("Could not open file");           // Helper vars         std::string line, colname;         int val;           // Read the column names         if (myFile.good())         {             // Extract the first line in the file             std::getline(myFile, line);               // Create a stringstream from line             std::stringstream ss(line);               // Extract each column name             while (std::getline(ss, colname, ',')) {                   // Initialize and add <colname, int vector> pairs to result                 result.push_back({ colname, std::vector<int> {} });             }         }           // Read data, line by line         while (std::getline(myFile, line))         {             // Create a stringstream of the current line             std::stringstream ss(line);               // Keep track of the current column index             int colIdx = 0;               // Extract each integer             while (ss >> val) {                   // Add the current integer to the 'colIdx' column's values vector                 result.at(colIdx).second.push_back(val);                   // If the next token is a comma, ignore it and move on                 if (ss.peek() == ',') ss.ignore();                   // Increment the column index                 colIdx++;             }         }           // Close file         myFile.close();           return result;     }     /**      * @brief 写.      *      */     void CSVfilemanagement::create()     {         // file pointer         fstream fout;           // opens an existing csv file or creates a new file.         fout.open("reportcard.csv", ios::out | ios::app);           cout << "Enter the details of students:"             << " roll(序号） name（姓名） maths(数学） phy（物理） chem（化学） bio（生物）"             << endl;           int i, roll, phy, chem, math, bio;         string name;         int num = 0;         char yes = 'Y';           while (1)         {             cout << "序号" << endl;             cin >> roll;             cout << "姓名" << endl;             cin >> name;             cout << "数学" << endl;             cin >> math;             cout << "物理" << endl;             cin >> phy;             cout << "化学" << endl;             cin >> chem;             cout << "生物" << endl;             cin >> bio;               // Insert the data to file             fout << roll << ", "                 << name << ", "                 << math << ", "                 << phy << ", "                 << chem << ", "                 << bio                 << "\n";               cout << "是否继续输入学生信息：(Y/N)" << endl;             cin >> yes;             if (yes == 'N' || yes == 'n')             {                 break;             }               num++;         }           // Read the input         /*         for (i = 0; i < 1; i++) {             cout << "序号" << endl;             cin >> roll;             cout << "姓名" << endl;             cin >> name;             cout << "数学" << endl;             cin >> math;             cout << "物理" << endl;             cin >> phy;             cout << "化学" << endl;             cin >> chem;             cout << "生物" << endl;             cin >> bio;               // Insert the data to file             fout << roll << ", "                 << name << ", "                 << math << ", "                 << phy << ", "                 << chem << ", "                 << bio                 << "\n";         }         */         fout.close();     }     /// <summary>     ///     /// </summary>     /// <param name="line_data"></param>     void CSVfilemanagement::DisplayRowCsv(std::vector<std::string> line_data)     {        std::cout << line_data[0]<<"\t\t"             << line_data[1] << "\t\t"             << line_data[2] << "\t\t"             << line_data[3] << "\t\t"             << line_data[4] << "\t\t"             << line_data[5]             << std::endl;        /*  cout << "Details of Roll " << line_data[0] << " : \n";         cout << "Name: " << line_data[1] << "\n";         cout << "Maths: " << line_data[2] << "\n";         cout << "Physics: " << line_data[3] << "\n";         cout << "Chemistry: " << line_data[4] << "\n";         cout << "Biology: " << line_data[5] << "\n";*/              }     /// <summary>     /// 读全部记录     /// </summary>     void CSVfilemanagement::readAll()     {           // File pointer         fstream fin;           // Open an existing file         fin.open("reportcard.csv", ios::in);             if (!fin.is_open())         {             std::cout << "Error: opening file fail（没有找到文件）" << std::endl;             std::exit(1);         }           // Get the roll number         // of which the data is required         int rollnum, roll2, count = 0;         cout << "Enter the roll number（行号） "             << "of the student to display details: ";         cin >> rollnum;           // Read the Data from the file         // as String Vector         vector<string> row;         string line, word, temp,headtile;             std::vector<std::string> words; //声明一个字符串向量         std::vector<std::string> headwords;         std::istringstream sin;           // std::string word;          // ------------读取数据-----------------          // 读取标题行               std::getline(fin, line);         sin.str(line);         while (std::getline(sin, headtile, ','))//将字符串流sin中的字符读到field字符串中，以逗号为分隔符         {             headwords.push_back(headtile);         }         for (auto headstr : headwords)         {             cout << headstr << "\t\t";         }         cout << "\n";         /*         cout << headwords[0] << "\t\t"             << headwords[1] << "\t\t"             << headwords[2] << "\t\t"             << headwords[3] << "\t\t"             << headwords[4] << "\t\t"             << headwords[5] << "\n";*/         // 按行读取数据         while (std::getline(fin, line))         {             // 清空vector,只存当前行的数据             words.clear();             sin.clear();             sin.str(line);             while (std::getline(sin, word, ',')) //将字符串流sin中的字符读到field字符串中，以逗号为分隔符             {                 //std::cout << word << std::endl;                 words.push_back(word); //将每一格中的数据逐个push             }               DisplayRowCsv(words);         }       }     /**      * @brief 读、查找.      *      */     void CSVfilemanagement::read_record()     {           // File pointer         fstream fin;           // Open an existing file         fin.open("reportcard.csv", ios::in);             if (!fin.is_open())         {             std::cout << "Error: opening file fail（没有找到文件）" << std::endl;             std::exit(1);         }           // Get the roll number         // of which the data is required         int rollnum, roll2, count = 0;         cout << "Enter the roll number（行号） "             << "of the student to display details: ";         cin >> rollnum;           // Read the Data from the file         // as String Vector         vector<string> row;         string line, word, temp;                               while (fin >> temp) {               row.clear();             //行             //line = rollnum;             // read an entire row and             // store it in a string variable 'line'             //读取标题                                         // used for breaking words             stringstream s(line);                           // read every column data of a row and             // store it in a string variable, 'word'             //std::getline(std::cin, name);            // if (!word.empty())             //{                 while (std::getline(s, word, ',')) {                       // add all the column data                     // of a row to a vector                     row.push_back(word);                 }            // }             // convert string to integer for comparision             roll2 = stoi(row[0]);               // Compare the roll number             if (roll2 == rollnum) {                   // Print the found data                 count = 1;                 cout << "Details of Roll " << row[0] << " : \n";                 cout << "Name: " << row[1] << "\n";                 cout << "Maths: " << row[2] << "\n";                 cout << "Physics: " << row[3] << "\n";                 cout << "Chemistry: " << row[4] << "\n";                 cout << "Biology: " << row[5] << "\n";                 break;             }                       }         if (count == 0)             cout << "Record not found\n";         fin.close();       }     /// <summary>     ///     /// </summary>     void CSVfilemanagement::update_recode()     {           // File pointer         fstream fin, fout;           // Open an existing record         fin.open("reportcard.csv", ios::in);           // Create a new file to store updated data         fout.open("reportcardnew.csv", ios::out);           int rollnum, roll1, marks, count = 0, i;         char sub;         int index, new_marks;         string line, word;         vector<string> row;           // Get the roll number from the user         cout << "Enter the roll number "             << "of the record to be updated: ";         cin >> rollnum;           // Get the data to be updated         cout << "Enter the subject "             << "to be updated(M/P/C/B): ";         cin >> sub;           // Determine the index of the subject         // where Maths has index 2,         // Physics has index 3, and so on         if (sub == 'm' || sub == 'M')             index = 2;         else if (sub == 'p' || sub == 'P')             index = 3;         else if (sub == 'c' || sub == 'C')             index = 4;         else if (sub == 'b' || sub == 'B')             index = 5;         else {             cout << "Wrong choice.Enter again\n";             this->update_recode();// update_record();         }           // Get the new marks         cout << "Enter new marks: ";         cin >> new_marks;           // Traverse the file         while (!fin.eof()) {               row.clear();               getline(fin, line);             stringstream s(line);             //std::getline();             while (std::getline(s, word, ',')) {                 row.push_back(word);             }               roll1 = stoi(row[0]);             int row_size = row.size();               if (roll1 == rollnum) {                 count = 1;                 stringstream convert;                   // sending a number as a stream into output string                 convert << new_marks;                   // the str() converts number into string                 row[index] = convert.str();                   if (!fin.eof()) {                     for (i = 0; i < row_size - 1; i++) {                           // write the updated data                         // into a new file 'reportcardnew.csv'                         // using fout                         fout << row[i] << ", ";                     }                       fout << row[row_size - 1] << "\n";                 }             }             else {                 if (!fin.eof()) {                     for (i = 0; i < row_size - 1; i++) {                           // writing other existing records                         // into the new file using fout.                         fout << row[i] << ", ";                     }                       // the last column data ends with a '\n'                     fout << row[row_size - 1] << "\n";                 }             }             if (fin.eof())                 break;         }         if (count == 0)             cout << "Record not found\n";           fin.close();         fout.close();           // removing the existing file         remove("reportcard.csv");           // renaming the updated file with the existing file name         rename("reportcardnew.csv", "reportcard.csv");     }     /// <summary>     ///     /// </summary>     void CSVfilemanagement::delete_record()     {           // Open FIle pointers         fstream fin, fout;           // Open the existing file         fin.open("reportcard.csv", ios::in);           // Create a new file to store the non-deleted data         fout.open("reportcardnew.csv", ios::out);           int rollnum, roll1, marks, count = 0, i;         char sub;         int index, new_marks;         string line, word;         vector<string> row;           // Get the roll number         // to decide the data to be deleted         cout << "Enter the roll number "             << "of the record to be deleted: ";         cin >> rollnum;           // Check if this record exists         // If exists, leave it and         // add all other data to the new file         while (!fin.eof()) {               row.clear();             getline(fin, line);             stringstream s(line);               while (std::getline(s, word, ',')) {                 row.push_back(word);             }               int row_size = row.size();             roll1 = stoi(row[0]);               // writing all records,             // except the record to be deleted,             // into the new file 'reportcardnew.csv'             // using fout pointer             if (roll1 != rollnum) {                 if (!fin.eof()) {                     for (i = 0; i < row_size - 1; i++) {                         fout << row[i] << ", ";                     }                     fout << row[row_size - 1] << "\n";                 }             }             else {                 count = 1;             }             if (fin.eof())                 break;         }         if (count == 1)             cout << "Record deleted\n";         else             cout << "Record not found\n";           // Close the pointers         fin.close();         fout.close();           // removing the existing file         remove("reportcard.csv");           // renaming the new file with the existing file name         rename("reportcardnew.csv", "reportcard.csv");     }     }

　　

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/// <summary> /// /// </summary> void Geovin::Displaycsv() {       // Open file     csvstream csvin("input.csv");       // Rows have key = column name, value = cell datum     map<string, string> row;           std::map<std::string, string>::iterator it = row.begin();     // Extract the "animal" column    cout << "动物名称" << "\t\t" << "动物类型" << endl;     while (csvin >> row) {                    cout << row["name"]<<"\t\t"<< row["animal"] << "\n";               }       while (it != row.end())     {         cout << "I:" << it->first << it->second << endl;         //string st = it->first;         //cout << st << endl;         //break;     }   }   /// <summary> /// /// </summary> void Geovin::DisplayAtemDemo() {     ATMdemo atem;     atem.setATM(); }       /// <summary> /// csv 操作 /// </summary> void Geovin::CsvCreate() {     CSVfilemanagement csv;         //string geovindu=csv.readFileIntoDuString("reportcard.csv");     //csv.getReadFile();       //csv.create();     csv.readAll();     //csv.read_record(); }

　　

调用：

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geovin.Displaycsv();       //ATM     //geovin.DisplayAtemDemo();       geovin.CsvCreate();

　　

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