我需要在c++中加载和使用CSV文件数据。在这一点上,它实际上只是一个以逗号分隔的解析器(即不用担心转义新行和逗号)。主要需要的是逐行解析器,它将在每次调用方法时为下一行返回一个向量。
我发现这篇文章看起来很有前途: http://www.boost.org/doc/libs/1_35_0/libs/spirit/example/fundamental/list_parser.cpp
我从未使用过Boost's Spirit,但我愿意尝试一下。但前提是我忽略了一个更直接的解决方案。
我需要在c++中加载和使用CSV文件数据。在这一点上,它实际上只是一个以逗号分隔的解析器(即不用担心转义新行和逗号)。主要需要的是逐行解析器,它将在每次调用方法时为下一行返回一个向量。
我发现这篇文章看起来很有前途: http://www.boost.org/doc/libs/1_35_0/libs/spirit/example/fundamental/list_parser.cpp
我从未使用过Boost's Spirit,但我愿意尝试一下。但前提是我忽略了一个更直接的解决方案。
当前回答
我写了一个只有头文件的c++ 11 CSV解析器。它经过了良好的测试,快速,支持整个CSV规范(带引号的字段,引号中的分隔符/结束符,引号转义等),并且可以配置为不符合规范的CSV。
配置是通过一个流畅的接口完成的:
// constructor accepts any input stream
CsvParser parser = CsvParser(std::cin)
.delimiter(';') // delimited by ; instead of ,
.quote('\'') // quoted fields use ' instead of "
.terminator('\0'); // terminated by \0 instead of by \r\n, \n, or \r
解析只是一个基于范围的for循环:
#include <iostream>
#include "../parser.hpp"
using namespace aria::csv;
int main() {
std::ifstream f("some_file.csv");
CsvParser parser(f);
for (auto& row : parser) {
for (auto& field : row) {
std::cout << field << " | ";
}
std::cout << std::endl;
}
}
其他回答
下面是读取矩阵的代码,注意你在matlab中也有一个csvwrite函数
void loadFromCSV( const std::string& filename )
{
std::ifstream file( filename.c_str() );
std::vector< std::vector<std::string> > matrix;
std::vector<std::string> row;
std::string line;
std::string cell;
while( file )
{
std::getline(file,line);
std::stringstream lineStream(line);
row.clear();
while( std::getline( lineStream, cell, ',' ) )
row.push_back( cell );
if( !row.empty() )
matrix.push_back( row );
}
for( int i=0; i<int(matrix.size()); i++ )
{
for( int j=0; j<int(matrix[i].size()); j++ )
std::cout << matrix[i][j] << " ";
std::cout << std::endl;
}
}
c++ String工具箱库(StrTk)有一个令牌网格类,它允许你从文本文件、字符串或字符缓冲区加载数据,并以行-列的方式解析/处理它们。
您可以指定行分隔符和列分隔符,或者只使用默认值。
void foo()
{
std::string data = "1,2,3,4,5\n"
"0,2,4,6,8\n"
"1,3,5,7,9\n";
strtk::token_grid grid(data,data.size(),",");
for(std::size_t i = 0; i < grid.row_count(); ++i)
{
strtk::token_grid::row_type r = grid.row(i);
for(std::size_t j = 0; j < r.size(); ++j)
{
std::cout << r.get<int>(j) << "\t";
}
std::cout << std::endl;
}
std::cout << std::endl;
}
更多的例子可以在这里找到
我写了一个很好的解析CSV文件的方法,我认为我应该把它作为一个答案:
#include <algorithm>
#include <fstream>
#include <iostream>
#include <stdlib.h>
#include <stdio.h>
struct CSVDict
{
std::vector< std::string > inputImages;
std::vector< double > inputLabels;
};
/**
\brief Splits the string
\param str String to split
\param delim Delimiter on the basis of which splitting is to be done
\return results Output in the form of vector of strings
*/
std::vector<std::string> stringSplit( const std::string &str, const std::string &delim )
{
std::vector<std::string> results;
for (size_t i = 0; i < str.length(); i++)
{
std::string tempString = "";
while ((str[i] != *delim.c_str()) && (i < str.length()))
{
tempString += str[i];
i++;
}
results.push_back(tempString);
}
return results;
}
/**
\brief Parse the supplied CSV File and obtain Row and Column information.
Assumptions:
1. Header information is in first row
2. Delimiters are only used to differentiate cell members
\param csvFileName The full path of the file to parse
\param inputColumns The string of input columns which contain the data to be used for further processing
\param inputLabels The string of input labels based on which further processing is to be done
\param delim The delimiters used in inputColumns and inputLabels
\return Vector of Vector of strings: Collection of rows and columns
*/
std::vector< CSVDict > parseCSVFile( const std::string &csvFileName, const std::string &inputColumns, const std::string &inputLabels, const std::string &delim )
{
std::vector< CSVDict > return_CSVDict;
std::vector< std::string > inputColumnsVec = stringSplit(inputColumns, delim), inputLabelsVec = stringSplit(inputLabels, delim);
std::vector< std::vector< std::string > > returnVector;
std::ifstream inFile(csvFileName.c_str());
int row = 0;
std::vector< size_t > inputColumnIndeces, inputLabelIndeces;
for (std::string line; std::getline(inFile, line, '\n');)
{
CSVDict tempDict;
std::vector< std::string > rowVec;
line.erase(std::remove(line.begin(), line.end(), '"'), line.end());
rowVec = stringSplit(line, delim);
// for the first row, record the indeces of the inputColumns and inputLabels
if (row == 0)
{
for (size_t i = 0; i < rowVec.size(); i++)
{
for (size_t j = 0; j < inputColumnsVec.size(); j++)
{
if (rowVec[i] == inputColumnsVec[j])
{
inputColumnIndeces.push_back(i);
}
}
for (size_t j = 0; j < inputLabelsVec.size(); j++)
{
if (rowVec[i] == inputLabelsVec[j])
{
inputLabelIndeces.push_back(i);
}
}
}
}
else
{
for (size_t i = 0; i < inputColumnIndeces.size(); i++)
{
tempDict.inputImages.push_back(rowVec[inputColumnIndeces[i]]);
}
for (size_t i = 0; i < inputLabelIndeces.size(); i++)
{
double test = std::atof(rowVec[inputLabelIndeces[i]].c_str());
tempDict.inputLabels.push_back(std::atof(rowVec[inputLabelIndeces[i]].c_str()));
}
return_CSVDict.push_back(tempDict);
}
row++;
}
return return_CSVDict;
}
这是一个旧线程,但它仍然在搜索结果的顶部,所以我添加我的解决方案使用std::stringstream和一个简单的字符串替换方法由Yves Baumes我在这里找到。
下面的例子将逐行读取文件,忽略以//开头的注释行,并将其他行解析为字符串、int和double的组合。Stringstream进行解析,但希望字段由空格分隔,因此我使用stringreplace首先将逗号转换为空格。它可以处理制表符,但不处理带引号的字符串。
坏的或丢失的输入被简单地忽略,这可能是好事,也可能不是好事,这取决于您的情况。
#include <string>
#include <sstream>
#include <fstream>
void StringReplace(std::string& str, const std::string& oldStr, const std::string& newStr)
// code by Yves Baumes
// http://stackoverflow.com/questions/1494399/how-do-i-search-find-and-replace-in-a-standard-string
{
size_t pos = 0;
while((pos = str.find(oldStr, pos)) != std::string::npos)
{
str.replace(pos, oldStr.length(), newStr);
pos += newStr.length();
}
}
void LoadCSV(std::string &filename) {
std::ifstream stream(filename);
std::string in_line;
std::string Field;
std::string Chan;
int ChanType;
double Scale;
int Import;
while (std::getline(stream, in_line)) {
StringReplace(in_line, ",", " ");
std::stringstream line(in_line);
line >> Field >> Chan >> ChanType >> Scale >> Import;
if (Field.substr(0,2)!="//") {
// do your stuff
// this is CBuilder code for demonstration, sorry
ShowMessage((String)Field.c_str() + "\n" + Chan.c_str() + "\n" + IntToStr(ChanType) + "\n" +FloatToStr(Scale) + "\n" +IntToStr(Import));
}
}
}
不管怎样,下面是我的实现。它处理wstring输入,但是可以很容易地调整为string。它不处理字段中的换行符(因为我的应用程序也不这样做,但添加它的支持并不太难),它不符合RFC中的“\r\n”行尾(假设您使用std::getline),但它确实正确地处理空格修剪和双引号(希望如此)。
using namespace std;
// trim whitespaces around field or double-quotes, remove double-quotes and replace escaped double-quotes (double double-quotes)
wstring trimquote(const wstring& str, const wstring& whitespace, const wchar_t quotChar)
{
wstring ws;
wstring::size_type strBegin = str.find_first_not_of(whitespace);
if (strBegin == wstring::npos)
return L"";
wstring::size_type strEnd = str.find_last_not_of(whitespace);
wstring::size_type strRange = strEnd - strBegin + 1;
if((str[strBegin] == quotChar) && (str[strEnd] == quotChar))
{
ws = str.substr(strBegin+1, strRange-2);
strBegin = 0;
while((strEnd = ws.find(quotChar, strBegin)) != wstring::npos)
{
ws.erase(strEnd, 1);
strBegin = strEnd+1;
}
}
else
ws = str.substr(strBegin, strRange);
return ws;
}
pair<unsigned, unsigned> nextCSVQuotePair(const wstring& line, const wchar_t quotChar, unsigned ofs = 0)
{
pair<unsigned, unsigned> r;
r.first = line.find(quotChar, ofs);
r.second = wstring::npos;
if(r.first != wstring::npos)
{
r.second = r.first;
while(((r.second = line.find(quotChar, r.second+1)) != wstring::npos)
&& (line[r.second+1] == quotChar)) // WARNING: assumes null-terminated string such that line[r.second+1] always exist
r.second++;
}
return r;
}
unsigned parseLine(vector<wstring>& fields, const wstring& line)
{
unsigned ofs, ofs0, np;
const wchar_t delim = L',';
const wstring whitespace = L" \t\xa0\x3000\x2000\x2001\x2002\x2003\x2004\x2005\x2006\x2007\x2008\x2009\x200a\x202f\x205f";
const wchar_t quotChar = L'\"';
pair<unsigned, unsigned> quot;
fields.clear();
ofs = ofs0 = 0;
quot = nextCSVQuotePair(line, quotChar);
while((np = line.find(delim, ofs)) != wstring::npos)
{
if((np > quot.first) && (np < quot.second))
{ // skip delimiter inside quoted field
ofs = quot.second+1;
quot = nextCSVQuotePair(line, quotChar, ofs);
continue;
}
fields.push_back( trimquote(line.substr(ofs0, np-ofs0), whitespace, quotChar) );
ofs = ofs0 = np+1;
}
fields.push_back( trimquote(line.substr(ofs0), whitespace, quotChar) );
return fields.size();
}