如何从 CSV 文件中获取数据，并将数据解析为两个逗号之间的 INT？

Posted 2023-02-22

【中文标题】如何从 CSV 文件中获取数据，并将数据解析为两个逗号之间的 INT？

【英文标题】：How do I take data from a CSV file, and parse the data into an INT between two commas?

【发布时间】：2017-07-31 23:10:44

【问题描述】：

首先，很抱歉这个问题可能不具体，因为这是我第一次问 *** 的问题。

我会开始做生意，我正在做一个项目，它读取一个文件（特别是 CSV），然后将某些数据从那里保存到一个 Int 中，我稍后会搞砸。

基本上，我的代码目前如下：

            if (!infile) 
            cout << "You entered something that cannot be opened, please try again." << endl;
            Continue = true;
        
        else 
            while (infile.good()) 
                getline(infile, value, ','); // read a string until next comma
                cout << string(value, 1, value.length() - 2); // display value removing the first and the last character from it
            
            Continue = false;
        
    

到目前为止，这会读取数据并输出如下所示的行：

    2014-01-03,"2014","01","03","†","-12.8","","-31.0","","-21.9","","39.9","","0.0","","","M","","M","0.0","","","","","","<31",""
2014-01-04,"2014","01","04","†","-2.3","","-12.8","","-7.6","","25.6","","0.0","","","M","","M","2.9","","40","","18","","39",""
2014-01-05,"2014","01","05","†","-2.1","","-4.1","","-3.1","","21.1","","0.0","","","M","","M","16.2","","52","","8","","32",""

我需要的信息在第 5 个和第 6 个逗号之间（它代表一天的平均温度），我需要将这两个逗号之间的信息放入某种 int 中。

同样，第 3 和第 4 个逗号之间是天，稍后我需要用它来计算每个月的平均温度，所以我也需要计算出来。

有谁知道这样做的正确方法？不幸的是，我对字符串解析的了解还不够。

【问题讨论】：

请先搜索再进行。通过在互联网上搜索“*** c++ 读取文件逗号分隔”可以找到大量类似的问题

【参考方案1】：

首先，第 5 和第 6 个逗号之间的值是浮点数 - 您应该将其转换为 float 或 double。

那么，

如果两者都

你总是有一个“。”作为浮点数中的分隔符 您可以接受 C++17 或更高版本的语言 使用

std::from_chars

(https://en.cppreference.com/w/cpp/utility/from_chars)

如果不是，请考虑以下几点：

对于有符号整数 -

std::stoi

/

std::stol

/

std::stoll

(https://en.cppreference.com/w/cpp/string/basic_string/stol) 和

std::strtol

/

std::strtoll

(https://en.cppreference.com/w/cpp/string/byte/strtol) 对于无符号整数 -

std::stoul

/

std::stoul

(https://en.cppreference.com/w/cpp/string/basic_string/stoul) 和

std::strtoul

/

std::strtoull

(https://en.cppreference.com/w/cpp/string/byte/strtoul) 对于浮点数 -

std::stof

/

std::stod

/

std::stold

(https://en.cppreference.com/w/cpp/string/basic_string/stof)，

std::strtof

/

std::strtod

/

std::strtold

(https://en.cppreference.com/w/cpp/string/byte/strtof) 和宽字符串

std ::wcstof

/

std::wcstod

/

std::wcstold

(https://en.cppreference.com/w/cpp/string/wide/wcstof)

如果您的编译器不支持上述功能，您唯一的选择是 atoi/atol (https://en.cppreference.com/w/cpp/string/byte/atoi) 和 atof (https://en.cppreference.com/w/cpp/string/byte/atof) 和 sscanf (https://en.cppreference.com/w/cpp/io/c/fscanf)。