CSV Example: Complete Code

By Michael Morin, About.com Guide

The following is the complete code for the "CSV Parsing" articles you can find here. As noted in the articles, Ruby does come with a better (faster, more correct, more complete) CSV library, so this code is not intended to be used in a production environment, but merely serve as an example.

#!/usr/bin/env ruby

# Parse a CSV file with column names.
# The first line of the file is assumed
# to be the column names, and also defines
# the number of columns.  Returns an
# array of hashes.
def csv(file)
  File.open(file) do|f|
    columns = f.readline.chomp.split(',')

    table = []
    until f.eof?
      row = f.readline.chomp.split(',')
      row = columns.zip(row).flatten
      table << Hash[*row]
    end

    return columns, table
  end
end

# Print a grade book from a CSV file.
# A grade book is alphabetized by first
# and last name and the columns are
# aligned properly.
columns, grades = csv(ARGV[0])

# Sort names by last name, then first name
grades.sort! do|a,b|
  a['Name'].split(' ').reverse.join(' ') <=> b['Name'].split(' ').reverse.join(' ')
end

# Determine column widths
column_widths = {}
columns.each do|c|
  column_widths[c] = [ c.length, *grades.map{|g| g[c].length } ].max
end

# Make the format string
format = columns.map{|c| "%-#{column_widths[c]}s" }.join(' | ')

# Print the table
puts format % columns
puts format.tr(' |', '-+') % column_widths.values.map{|v| '-'*v }

grades.each do|g|
  puts format % columns.map{|c| g[c] }
end