CSVファイルでPythonからC++への行列データの受け渡し

はじめに

Pythonで計算した結果の4×3の行列を,C++から読みたいと思い、その方法をまとめました。

書き込み(Python)

write.py

import csv

data = [[1,2,3,4],[5,6,7,8],[9,10,11,12]]

with open('test.csv', 'w') as file:
    writer = csv.writer(file, lineterminator='\n')
    writer.writerows(data)

読み込み(Python)

read.py

import csv
import pprint

with open('test.csv') as f:
    reader = csv.reader(f, quoting=csv.QUOTE_NONNUMERIC)
    l_f = [row for row in reader]

print(l_f) 

読み込み(C++)

read.cpp

#include <fstream>
#include <string>
#include <sstream>
#include <vector>
#include <iostream>

std::vector<std::string> split(std::string& input, char delimiter)
{
  std::istringstream stream(input);
  std::string field;
  std::vector<std::string> result;
  while (getline(stream, field, delimiter)) {
    result.push_back(field);
  }
  return result;
}

int main(){

  std::string file("test.csv");

  std::ifstream ifs(file);

  std::string line;
  std::vector<std::string> strvec = split(line, ',');

  float m11,m12,m13,m14;
  float m21,m22,m23,m24;
  float m31,m32,m33,m34;

  getline(ifs, line);
  strvec = split(line, ',');
  m11 = std::stof(strvec.at(0));
  m12 = std::stof(strvec.at(1));
  m13 = std::stof(strvec.at(2));
  m14 = std::stof(strvec.at(3));

  getline(ifs, line);
  strvec = split(line, ',');
  m21 = std::stof(strvec.at(0));
  m22 = std::stof(strvec.at(1));
  m23 = std::stof(strvec.at(2));
  m24 = std::stof(strvec.at(3));

  getline(ifs, line);
  strvec = split(line, ',');
  m31 = std::stof(strvec.at(0));
  m32 = std::stof(strvec.at(1));
  m33 = std::stof(strvec.at(2));
  m34 = std::stof(strvec.at(3));

  std::cout << m11 << " " << m12 << " " << m13 << " " << m14 << std::endl;
  std::cout << m21 << " " << m22 << " " << m23 << " " << m24 << std::endl;
  std::cout << m31 << " " << m32 << " " << m33 << " " << m34 << std::endl;

return 0;
}