Append Row to CSV File Ruby 1.9 CSV Lib

How to append data to csv file

``a'' Write-only, starts at end of file if file exists, otherwise
creates a new file for writing.

``a+'' Read-write, starts at end of
file if file exists, otherwise creates a new file for reading and
writing

use CSV.open("participants_info.csv", "a+")

write csv in ruby 1.9 and CSV::Writer

The csv library is still there, but CSV::Writer is not. According to the csv.rb in 1.9.0:

# I'm sure I'll miss something, but I'll try to mention most of the major
# differences I am aware of, to help others quickly get up to speed:
#
# === CSV Parsing
#
# * This parser is m17n aware.  See CSV for full details.
# * This library has a stricter parser and will throw MalformedCSVErrors on
#   problematic data.
# * This library has a less liberal idea of a line ending than CSV.  What you
#   set as the <tt>:row_sep</tt> is law.  It can auto-detect your line endings
#   though.
# * The old library returned empty lines as <tt>[nil]</tt>.  This library calls
#   them <tt>[]</tt>.
# * This library has a much faster parser.
#
# === Interface
#
# * CSV now uses Hash-style parameters to set options.
# * CSV no longer has generate_row() or parse_row().
# * The old CSV's Reader and Writer classes have been dropped.
# * CSV::open() is now more like Ruby's open().
# * CSV objects now support most standard IO methods.
# * CSV now has a new() method used to wrap objects like String and IO for
#   reading and writing.
# * CSV::generate() is different from the old method.
# * CSV no longer supports partial reads.  It works line-by-line.
# * CSV no longer allows the instance methods to override the separators for
#   performance reasons.  They must be set in the constructor.

A little later on, there's an example of how to write line-by-line (as well as other methods of writing):

# === To a File
#
#   CSV.open("path/to/file.csv", "wb") do |csv|
#     csv << ["row", "of", "CSV", "data"]
#     csv << ["another", "row"]
#     # ...
#   end

Split output data using CSV in Ruby 1.9

The short answer is "no". You'll want to adjust your current code to split up the set and then dump each subset to a different file. This ought to be pretty close:

export_rows.each_slice(1000).with_index do |rows, idx|
  CSV.open("#{PATH_TO_EXPORT_FILE}/newexport-#{idx.to_s}.csv", "w+", :col_sep => '|', :headers => true) do |f|
    rows.each { |row| f << row }
  end
end

How write into CSV file properly

csv << "\n"

Stackoverflow requires 30 characters in an answer, but I don't know what more to say.

Output array to CSV in Ruby

To a file:

require 'csv'
CSV.open("myfile.csv", "w") do |csv|
  csv << ["row", "of", "CSV", "data"]
  csv << ["another", "row"]
  # ...
end

To a string:

require 'csv'
csv_string = CSV.generate do |csv|
  csv << ["row", "of", "CSV", "data"]
  csv << ["another", "row"]
  # ...
end

Here's the current documentation on CSV: http://ruby-doc.org/stdlib/libdoc/csv/rdoc/index.html

Convert CSV column of strings to integers with CSV lib in Ruby 1.9

Aaron, just change the row and write it to your new file like this

require 'csv'

File.open('modified.csv', 'w') do |csv|
  CSV.foreach('original.csv', :headers => true) do |row|
    row['Estimated Weekend Gross'] = row['Estimated Weekend Gross'].delete(',').to_i
    row['Cume'] = row['Cume'].delete(',').to_i
    csv << row
  end
end

EDIT: if you want to save the headers in modified.csv you can do it like this, but there must be a shorter way without opening the file twice, if someone has a better solution for this ?

headers = CSV.open('original.csv', 'r', :headers => true).read.headers
CSV.open('modified.csv', 'w') do |csv|
  csv << headers
  CSV.foreach('original.csv', :headers => true) do |row|
    row['Estimated Weekend Gross'] = row['Estimated Weekend Gross'].delete(',').to_i
    row['Cume'] = row['Cume'].delete(',').to_i
    csv << row
  end
end

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