remove rows in file - Ruby

Question

What is a clever way to remove rows from a CSV file in ruby where a particular value exists in a particular row?

Here\'s an example of a file:

350 lbs.,          


        

Answer 1

Well, I don't think this example will get the answer you are looking for... but this would work...

tmp.txt =>

350 lbs., Outrigger Footprint, 61" x 53", Weight, 767 lbs., 300-2080
350 lbs., Outrigger Footprint, 61" x 53", Weight, 817 lbs., 300-2580
350 lbs., Outrigger Footprint, 61" x 53", Weight, 817 lbs., 300-2580
350 lbs., Outrigger Footprint, 69" x 61", Weight, 867 lbs., 300-3080
350 lbs., Outrigger Footprint, 69" x 61", Weight, 867 lbs., 300-3080

File.readlines('tmp.txt').uniq will return this:

350 lbs., Outrigger Footprint, 61" x 53", Weight, 767 lbs., 300-2080
350 lbs., Outrigger Footprint, 61" x 53", Weight, 817 lbs., 300-2580
350 lbs., Outrigger Footprint, 69" x 61", Weight, 867 lbs., 300-3080

So, you could also easily sort with Array fxns. Google ruby arrays and I'm sure you can learn how to choose if you want an entry according to a comparison to a desired string.

Answer 2

You can use this to get the unique lines in an array in a csv file

File.readlines("file.csv").uniq
=> ["350 lbs., Outrigger Footprint, 61\" x 53\", Weight, 767 lbs., 300-2080\n", "350 lbs., Outrigger Footprint, 61\" x 53\", Weight, 817 lbs., 300-2580\n", "350 lbs., Outrigger Footprint, 69\" x 61\", Weight, 867 lbs., 300-3080\n"]

To write it to a new file, you can open a file in write mode, write this into the file:

File.open("new_csv", "w+") { |file| file.puts File.readlines("csv").uniq }

For comparing values, you can use split function on ",", to access each column like this:

rows = File.readlines("csv").map(&:chomp) # equivalent to File.readlines.map { |f| f.chomp }
mapped_columns = rows.map { |r| r.split(",").map(&:strip) }
=> [["350 lbs.", " Outrigger Footprint", " 61\" x 53\"", " Weight", " 767 lbs.", " 300-2080"], ["350 lbs.", " Outrigger Footprint", " 61\" x 53\"", " Weight", " 817 lbs.", " 300-2580"], .....]
mapped_columns[0][5]
=> "300-2080"

If you want more functionality, you are better off installing FasterCSV gem.

Answer 3

You can also create a Hash which would NOT allow duplicate records as its entries . For example, the following code should help:

require 'optparse'
require 'csv'
require 'pp'

options = Hash.new

OptionParser.new do |opts|
    opts.banner = "Usage: remove_extras.rb [options] file1 ..."

    options[:input_file] = ''
    opts.on('-i', '--input_file FILENAME', 'File to have extra rows removed') do |file|
        options[:input_file] = file
    end

end.parse!
if File.exists?(options[:input_file])
    p "Parsing: #{options[:input_file]}"
        UniqFile=Hash.new    
        File.open(options[:input_file]).each do |row|
        UniqFile.store(row,row.hash)                
end
puts "please enter the output filename: \n"
aFile=File.open(gets.chomp, "a+")
UniqFile.each do|key,value| 
aFile.syswrite("#{key}")
end  

end