C++模仿Numpy常用文本文件读取、写入

经常用C++读入、写出（打印）矩阵数组，觉得要想办法自动解决一下这个问题。于是开始模仿Python的Numpy，矩阵暂时用vector<vector<double>>代替：

*目前是V0.1

实现功能主要如下：

• ReadTxt.h / ReadTxt.cpp
  • genFromtxt（支持分隔符和注释，制表符视为空格，返回vector<vector<double>>）
• WriteTxt.h / Writetxt.cpp
  • print（显示在屏幕上，fixed，可控制位数）
  • saveTxt（将vector<vector<double>>保存为文件，fixed，可控制位数）

更详细一点的说明见头文件函数定义注释

????ReadTxt.h

/*
@author: Kan Haoyu
@date: 2021/3/8
@function: Basic text Input
*/
#pragma once
#ifndef READTXT_H
#define READTXT_H
#include <iostream>
#include <fstream>
#include <sstream>
#include <vector>
#include <algorithm>
using namespace std;
// read a txt into a vector<vector<double>> ;
// line splited by split_char; 
// string after comment_char will be discarded; 
// line without contents(pure comment) will also be discarded
vector<vector<double>> genFromtxt(const string& file_path, const char split_char, const char comment_char);
// return a string where substring after comment_char will be discarded
string decommentString(const string& str, const char comment_char);
// split string with split_char into a vector<string>
vector<string> splitString(const string& str, const char split_char);
// convert vector<string> into vector<double>
vector<double> asDouble(const vector<string>& vec_str);
// replace all tab('t') with blankspace(' ') in a string and return the result
string replaceTabWithBlankspace(const string& str);
#endif

????ReadTxt.cpp

#include "ReadTxt.h"
vector<vector<double>> genFromtxt(const string& file_path, const char split_char, const char comment_char)
{
ifstream infile;
string line;
vector<vector<double>> res;
string line_replace_tab;
string line_decomment;
infile.open(file_path);
if (!infile) {
cerr << "Error! genFromtxt file_path is wrong" << endl;
exit(0);
}
while (true) {
if (infile.eof()) {
break;
}
getline(infile, line);
// 将't'替换为' '防止之后转换出错
line_replace_tab = replaceTabWithBlankspace(line);
// comment_char 
// 发现comment_char则舍弃其和其之后的字符
line_decomment = decommentString(line_replace_tab, comment_char);
// split_char
// 按split_char切分进入vector
// 每一line对应一个vector
vector<double> vec_i;
vector<string> vec_str_i;
vec_str_i = splitString(line_decomment, split_char);
vec_i = asDouble(vec_str_i);
// 不留空行
if (vec_i.size() == 0) {
continue;
}
res.push_back(vec_i);
}
return res;
}
string decommentString(const string& str, const char comment_char)
{
string res;
size_t found = str.find(comment_char);
if (found != string::npos) {
res = str.substr(0, found);
}
else {
res = str;
}
return res;
}
vector<string> splitString(const string & str, const char split_char)
{
vector<string> res;
stringstream spliter(str);
string buffer;
while (getline(spliter, buffer, split_char)) {
if (buffer.empty()) {
continue;
}
res.push_back(buffer);
}
return res;
}
vector<double> asDouble(const vector<string>& vec_str)
{
vector<double> res;
res.reserve(vec_str.size());//预留分配，加速作用
for (int i = 0; i < vec_str.size(); i++) {
double t = stod(vec_str.at(i));
res.push_back(t);
}
return res;
}
string replaceTabWithBlankspace(const string & str)
{
string res;
res = str;
replace(res.begin(), res.end(), 't', ' ');
return res;
}

????WriteTxt.h

/*
@author: Kan Haoyu
@date: 2021/3/8
@function: Basic vector output to text
*/
#pragma once
#ifndef WRITETXT_H
#define WRITETXT_H
#include <iostream>
#include <fstream>
#include <sstream>
#include <vector>
#include <iomanip>
using namespace std;
// print a vector<vector<double>> on screen with designated precision, default = 4
void print(const vector<vector<double>>& vec_vec, const int precision = 4);
// save a vector<vector<double>> as ascii in file_path with designated precision, default = 4
void saveTxt(const string& file_path, const vector<vector<double>>& vec_vec, const int precision = 4);
#endif

???? WriteTxt.cpp

#include "WriteTxt.h"
void print(const vector<vector<double>>& vec_vec, const int precision)
{
cout << fixed << setprecision(precision);
for (int i = 0; i < vec_vec.size(); i++) {
for (int j = 0; j < vec_vec[i].size(); j++) {
cout << (vec_vec.at(i)).at(j) << " | ";
}
cout << "n";
}
}
void saveTxt(const string & file_path, const vector<vector<double>>& vec_vec, const int precision)
{
ofstream outfile;
outfile.open(file_path);
if (!outfile) {
cerr << "Error! saveTxt fail open file_path" << endl;
exit(0);
}
outfile << fixed << setprecision(precision);
for (int i = 0; i < vec_vec.size(); i++) {
for (int j = 0; j < vec_vec[i].size(); j++) {
outfile << (vec_vec.at(i)).at(j) << " ";
}
outfile << "n";
}
}

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