How to read a CSV with no headers

Question

I have a CSV with the following data (no header)

12,2010,76
2,2000,45
12,1940,30

and I'm using the following CSVReader to read

using UnityEngine;
using System;
using System.Collections;
using System.Collections.Generic;
using System.Text.RegularExpressions;

public class CSVReader
{
    static string SPLIT_RE = @",(?=(?:[^""]*""[^""]*"")*(?![^""]*""))";
    static string LINE_SPLIT_RE = @"\r\n|\n\r|\n|\r";
    static char[] TRIM_CHARS = { '\"' };

    public static List<Dictionary<string, object>> Read(string file)
    {
        var list = new List<Dictionary<string, object>>();
        TextAsset data = Resources.Load (file) as TextAsset;

        var lines = Regex.Split (data.text, LINE_SPLIT_RE);

        if(lines.Length <= 1) return list;

        var header = Regex.Split(lines[0], SPLIT_RE);
        for(var i=1; i < lines.Length; i++) {

            var values = Regex.Split(lines[i], SPLIT_RE);
            if(values.Length == 0 ||values[0] == "") continue;

            var entry = new Dictionary<string, object>();
            for(var j=0; j < header.Length && j < values.Length; j++ ) {
                string value = values[j];
                value = value.TrimStart(TRIM_CHARS).TrimEnd(TRIM_CHARS).Replace("\\", "");
                object finalvalue = value;
                int n;
                float f;
                if(int.TryParse(value, out n)) {
                    finalvalue = n;
                } else if (float.TryParse(value, out f)) {
                    finalvalue = f;
                }
                entry[header[j]] = finalvalue;
            }
            list.Add (entry);
        }
        return list;
    }
}

The problem is this CSVReader uses List<Dictionary<string, object>> and so if there is no header information, the dictionary keys become either null or (less likely) an empty string. Both of these cases would lead to exception throwing when adding entries to the dictionary.

I can add the headers to the CSV file but that isn't the ideal solution.

Can you change the library to CsvHelper, its extemely fast and easy. — HariHaran
– HariHaran, Commented Nov 7, 2019 at 12:03
Even though I'm using Unity, I think i can. Just didn't know about it and how to read data using it. — Bárbara Peres
– Bárbara Peres, Commented Nov 7, 2019 at 12:08
This has everything you need joshclose.github.io/CsvHelper/getting-started — HariHaran
– HariHaran, Commented Nov 7, 2019 at 12:17

Wai Ha Lee · Accepted Answer · 2019-11-07 16:16:34Z

3

Firstly, there are almost certainly lots of ready-made libraries you could use for this task, which are probably available on NuGet. One of those might well be a better solution.

Nevertheless, working with what you've got already you could make an alternative version of the method which returns a simple list of objects, and remove the code from it which populates the headers. Something like this (untested, but I think it should work):

public static List<List<object>> ReadWithoutHeader(string file)
{
    var list = new List<List<object>>();
    TextAsset data = Resources.Load (file) as TextAsset;
    var lines = Regex.Split (data.text, LINE_SPLIT_RE);

    if(lines.Length <= 1) return list;

    for(var i=0; i < lines.Length; i++) {

        var values = Regex.Split(lines[i], SPLIT_RE);
        if(values.Length == 0 ||values[0] == "") continue;
        var entry = new List<object>();

        for(var j=0; j < values.Length; j++ ) {
            string value = values[j];
            value = value.TrimStart(TRIM_CHARS).TrimEnd(TRIM_CHARS).Replace("\\", "");
            object finalvalue = value;
            int n;
            float f;
            if(int.TryParse(value, out n)) {
                finalvalue = n;
            } else if (float.TryParse(value, out f)) {
                finalvalue = f;
            }
            entry.Add(finalvalue);
        }
        list.Add(entry);
    }
    return list;
}

edited Nov 7, 2019 at 16:16

Wai Ha Lee

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answered Nov 7, 2019 at 12:07

ADyson

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3 Comments

Bárbara Peres Over a year ago

In ReadWithoutHeader(string file) I get an error saying not all code paths return a value

ADyson Over a year ago

Sorry. If you compare it to the original you'll see that I just forgot to add return list; at the end. Did you spot that? I will amend the answer

Bárbara Peres Over a year ago

You spotted faster than me

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