How to Create a 2D Array from a CSV File

Write a 2d array to a csv file with delimiter

Use csv module by import csv also take a note you might need either writerow() or writerows().

What's the difference you may ask?

writerow takes an iterable of cells to write:

writerow([1,2,2])
->
1,2,2

writerows takes an iterable of iterables of cells to write:

writerows([[1,2,3],
           [4,5,6],
           [6,7,8]])
->
1,2,3
4,5,6
6,7,8

Which can be ofcourse be given as a variable. Like

a = [[1,2,3],[4,5,6],[6,7,8]]
writerows(a)

Conclusion writerow takes 1-dimensional data (one row), and writerows takes 2-dimensional data (multiple rows).

Program for you:

import csv

a = [[1,2,3,4],[5,6,7,8]]

with open("new_file.csv","w+") as my_csv:
    csvWriter = csv.writer(my_csv,delimiter=',')
    csvWriter.writerows(a)

Note open() takes two arguments here the file to be written and the mode.

What is a mode you may ask?

It specifies how the file should be opened. In my case w+ means open file my_file.csv if it exists if it doesn't then fine create a new one and write.

There are several modes choose one. Note: w+ overwrites everytime you use it. That is old data in file will be overwritten so if you want to just append use a. Take a look at this for more details on modes.File modes

Best way to save a CSV file of a 2 dimensional array or list in Python?

If testarray contains multiple rows. Use writerows instead of writerow

import csv

testarray = [["a", "b"], ["c", "d"]]

with open('test.csv', mode='w') as employee_file:
    employee_writer = csv.writer(employee_file, delimiter=',',  quotechar='"',
                                 quoting=csv.QUOTE_MINIMAL)
    employee_writer.writerows(testarray)

Converting CSV File Into 2D Array

I would just add the split result (String[]) to a List then if you really want it as a 2d array then convert it after the fact.

List<String[]> lines = new ArrayList<String[]>();
while ((thisLine = myInput.readLine()) != null) {
     lines.add(thisLine.split(";"));
}

// convert our list to a String array.
String[][] array = new String[lines.size()][0];
lines.toArray(array);

read .csv file into 2D-array

You don't need 2 loops in while loop, here is the solution.

public class array2D
{
    private static int[][] readArrayFromFile(String filename)
    {
        int[][] array = new int[9][9];
        try
        {
            Scanner myFileReader = new Scanner(new File(filename));

            int i = 0;
            while (myFileReader.hasNextLine())
            {

                String line = myFileReader.nextLine();
                String[] tokens = line.split(";");

                for (int j = 0; j < tokens.length; j++)
                {
                    array[i][j] = Integer.parseInt(tokens[j]);
                }
                i++;
            }
        }
        catch (FileNotFoundException e)
        {
            System.out.println(e.getMessage());
        }
        return array;
    }

    private static void printArray(int[][] inputArray)
    {
        for (int y = 0; y < inputArray.length; y++)
        {
            for (int x = 0; x < inputArray[y].length; x++)
            {
                System.out.print(inputArray[y][x] + "\t");
            }
            System.out.println();
        }
        System.out.println();
    }

    public static void main(String[] args)
    {
        String filename = "./src/test.csv";
        int[][] sudokuField = readArrayFromFile(filename);
        printArray(sudokuField);
    }
}

Write a 2D array to a CSV file in python

You need to transpose your array first

import numpy as np
arr = np.array([[0.0, 1.0, 2.0, 3.0],[5.0, 1.0, 3.0, 3.0],[1.0, 1.0, 3.0, 3.0 ]])
arr_t = arr.T
print(arr_t)

output

[[0. 5. 1.]
 [1. 1. 1.]
 [2. 3. 3.]
 [3. 3. 3.]]

Then follows as earlier.