How to map and edit a CSV file with Ruby

Question

Is there a way to edit a CSV file using the map method in Ruby? I know I can open a file using:

CSV.open("file.csv", "a+")

and add content to it, but I have to edit some specific lines.

The foreach method is only useful to read a file (correct me if I'm wrong).

I checked the Ruby CSV documentation but I can't find any useful info.

My CSV file has less than 1500 lines so I don't mind reading all the lines.

Answer 1

Another answer using each.with_index():

rows_array = CSV.read('sample.csv')

desired_indices = [3, 4, 5].sort # these are rows you would like to modify
rows_array.each.with_index(desired_indices[0]) do |row, index| 
  if desired_indices.include?(index)

    # modify over here
    rows_array[index][target_column] = 'modification'

  end
end

# now update the file
CSV.open('sample3.csv', 'wb') { |csv| rows_array.each{|row| csv << row}}

You can also use each_with_index {} insead of each.with_index {}