Changing field separator/delimiter in exported CSV using Ruby CSV - ruby

Is it possible to change the default field separator from comma to to some other character, e.g '|' for exporting?

Here's an example using a tab instead.
To a file:
CSV.open("myfile.csv", "w", {:col_sep => "\t"}) do |csv|
csv << ["row", "of", "CSV", "data"]
csv << ["another", "row"]
# ...
end
To a string:
csv_string = CSV.generate(:col_sep => "\t") 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

The previous CSV library was replaced with FasterCSV in Ruby 1.9.
require "csv"
output = CSV.read("test.csv").map do |row|
row.to_csv(:col_sep => "|")
end
puts output

CSV::Writer has a generate method, which accepts a separator string as argument.
#!/usr/bin/env ruby
# +++ ruby 1.8 version +++
require "csv"
outfile = File.open('csvout', 'wb')
CSV::Writer.generate(outfile, '|') do |csv|
csv << ['c1', nil, '', '"', "\r\n", 'c2']
end
outfile.close

Related

manipulating csv with ruby

I have a CSV from which I've removed the irrelevant data.
Now I need to split "Name and surname" into 2 columns by space but ignoring a 3rd column in case there are 3 names, then invert the order of the columns "Name and surname" and "Phone" (phone first) and then put them into a file ignoring the headers. I've never actually learned Ruby but I've played with Python 10 years ago. Can you help me? This is what I was able to do until now:
E.g.
require 'csv'
csv_table = CSV.read(ARGV[0], :headers => true)
keep = ["Name and surname", "Phone", "Email"]
new_csv_table = csv_table.by_col!.delete_if do |column_name,column_values|
!keep.include? column_name
end
new_csv_table.to_csv
Begin by creating a CSV file.
str =<<~END
Name and surname,Phone,Email
John Doe,250-256-3145,John#Doe.com
Marsha Magpie,250-256-3154,Marsha#Magpie.com
END
File.write('t_in.csv', str)
#=> 109
Initially, let's read the file, add two columns, "Name" and "Surname", and optionally delete the column, "Name and surname", without regard to column order.
First read the file into a CSV::Table object.
require 'csv'
tbl = CSV.read('t_in.csv', headers: true)
#=> #<CSV::Table mode:col_or_row row_count:3>
Add the new columns.
tbl.each do |row|
row["Name"], row["Surname"] = row["Name and surname"].split
end
#=> #<CSV::Table mode:col_or_row row_count:3>
Note that if row["Name and surname"] had equaled “John Paul Jones”, we would have obtained row["Name"] #=> “John” and row["Surname"] #=> “Paul”.
If the column "Name and surname" is no longer required we can delete it.
tbl.delete("Name and surname")
#=> ["John Doe", "Marsha Magpie"]
Write tbl to a new CSV file.
CSV.open('t_out.csv', "w") do |csv|
csv << tbl.headers
tbl.each { |row| csv << row }
end
#=> #<CSV::Table mode:col_or_row row_count:3>
Let's see what was written.
puts File.read('t_out.csv')
displays
Phone,Email,Name,Surname
250-256-3145,John#Doe.com,John,Doe
250-256-3154,Marsha#Magpie.com,Marsha,Magpie
Now let's rearrange the order of the columns.
header_order = ["Phone", "Name", "Surname", "Email"]
CSV.open('t_out.csv', "w") do |csv|
csv << header_order
tbl.each { |row| csv << header_order.map { |header| row[header] } }
end
puts File.read('t_out.csv')
#=> #<CSV::Table mode:col_or_row row_count:3>
displays
Phone,Name,Surname,Email
250-256-3145,John,Doe,John#Doe.com
250-256-3154,Marsha,Magpie,Marsha#Magpie.com

Read from a CSV file, multiply two columns, and then write back to the CSV file in ruby?

I have created csv file with values.I am able to read rows but don't know how to access individual values of a column.
require "csv"
CSV.open("file.csv", "w")
do |csv|
csv << ["val1", "val2","mul"]
csv << ["53", "27"]
csv<<["32","20"]
end
You probably need to ignore the header row if you have one. But the general idea is this:
CSV.open('dest.csv', 'w') do |csv|
csv << ["val1", "val2","mul"]
CSV.foreach('source.csv') do |row|
c1 = row[0]
c2 = row[1]
csv << [c1, c2, c1*c2]
end
end
If you have headers, you could do this:
CSV.open('dest.csv', 'w') do |csv|
csv << ["val1", "val2", "mul"]
CSV.foreach('source.csv', headers: true) do |row|
c1 = row['val1']
c2 = row['val2']
csv << [c1, c2, c1*c2]
end
end
You can use the one below for a non-ruby solution too:
awk -F "," '{print $1,$2,$1*$2}' source.csv > dest.csv

How to use CSV.open and CSV.foreach methods to convert specific data in a csv file?

The Old.csv file contains these headers, "article_category_id", "articleID", "timestamp", "udid", but some of the values in those columns are strings. So, I am trying to convert them to integers and store in another CSV file, New.csv. This is my code:
require 'csv'
require 'time'
CSV.foreach('New.csv', "wb", :write_headers=> true, :headers =>["article_category_id", "articleID", "timestamp", "udid"]) do |csv|
CSV.open('Old.csv', :headers=>true) do |row|
csv['article_category_id']=row['article_category_id'].to_i
csv['articleID']=row['articleID'].to_i
csv['timestamp'] = row['timestamp'].to_time.to_i unless row['timestamp'].nil?
unless udids.include?(row['udid'])
udids << row['udid']
end
csv['udid'] = udids.index(row['udid']) + 1
csv<<row
end
end
But, I am getting the following error: in 'foreach': ruby wrong number of arguments (3 for 1..2) (ArgumentError).
When I change the foreach to open, I get the following error: undefined method '[]' for #<CSV:0x36e0298> (NoMethodError). Why is that? And how can I resolve it? Thanks.
CSV#foreach does not accept file access rights as second parameter:
CSV.open('New.csv', :headers=>true) do |csv|
CSV.foreach('Old.csv',
:write_headers => true,
:headers => ["article_category_id", "articleID", "timestamp", "udid"]
) do |row|
row['article_category_id'] = row['article_category_id'].to_i
...
csv << row
end
end
CSV#open should be placed before foreach. You are to iterate the old one and produce the new one. Inside the loop you should change row and than append it to the output.
You can refer my code:
require 'csv'
require 'time'
CSV.open('New.csv', "wb") do |csv|
csv << ["article_category_id", "articleID", "timestamp", "udid"]
CSV.foreach('Old.csv', :headers=>true) do |row|
array = []
article_category_id=row['article_category_id'].to_i
articleID=row['articleID'].to_i
timestamp = row['timestamp'].to_i unless row['timestamp'].nil?
unless udids.include?(row['udid'])
udids << row['udid']
end
udid = udids.index(row['udid']) + 1
array << [article_category_id, articleID, timestamp, udid]
csv<<array
end
end
The problem with Vinh answer is that at the end array variable is an array which has array inside.
So what is inserted indo CVS looks like
[[article_category_id, articleID, timestamp, udid]]
And that is why you get results in double quotes.
Please try something like this:
require 'csv'
require 'time'
CSV.open('New.csv', "wb") do |csv|
csv << ["article_category_id", "articleID", "timestamp", "udid"]
CSV.foreach('Old.csv', :headers=>true) do |row|
article_category_id = row['article_category_id'].to_i
articleID = row['articleID'].to_i
timestamp = row['timestamp'].to_i unless row['timestamp'].nil?
unless udids.include?(row['udid'])
udids << row['udid']
end
udid = udids.index(row['udid']) + 1
output_row = [article_category_id, articleID, timestamp, udid]
csv << output_row
end
end

Output array to CSV in Ruby

It's easy enough to read a CSV file into an array with Ruby but I can't find any good documentation on how to write an array into a CSV file. Can anyone tell me how to do this?
I'm using Ruby 1.9.2 if that matters.
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
If you have an array of arrays of data:
rows = [["a1", "a2", "a3"],["b1", "b2", "b3", "b4"], ["c1", "c2", "c3"]]
Then you can write this to a file with the following, which I think is much simpler:
require "csv"
File.write("ss.csv", rows.map(&:to_csv).join)
I've got this down to just one line.
rows = [['a1', 'a2', 'a3'],['b1', 'b2', 'b3', 'b4'], ['c1', 'c2', 'c3'], ... ]
csv_str = rows.inject([]) { |csv, row| csv << CSV.generate_line(row) }.join("")
#=> "a1,a2,a3\nb1,b2,b3\nc1,c2,c3\n"
Do all of the above and save to a csv, in one line.
File.open("ss.csv", "w") {|f| f.write(rows.inject([]) { |csv, row| csv << CSV.generate_line(row) }.join(""))}
NOTE:
To convert an active record database to csv would be something like this I think
CSV.open(fn, 'w') do |csv|
csv << Model.column_names
Model.where(query).each do |m|
csv << m.attributes.values
end
end
Hmm #tamouse, that gist is somewhat confusing to me without reading the csv source, but generically, assuming each hash in your array has the same number of k/v pairs & that the keys are always the same, in the same order (i.e. if your data is structured), this should do the deed:
rowid = 0
CSV.open(fn, 'w') do |csv|
hsh_ary.each do |hsh|
rowid += 1
if rowid == 1
csv << hsh.keys# adding header row (column labels)
else
csv << hsh.values
end# of if/else inside hsh
end# of hsh's (rows)
end# of csv open
If your data isn't structured this obviously won't work
If anyone is interested, here are some one-liners (and a note on loss of type information in CSV):
require 'csv'
rows = [[1,2,3],[4,5]] # [[1, 2, 3], [4, 5]]
# To CSV string
csv = rows.map(&:to_csv).join # "1,2,3\n4,5\n"
# ... and back, as String[][]
rows2 = csv.split("\n").map(&:parse_csv) # [["1", "2", "3"], ["4", "5"]]
# File I/O:
filename = '/tmp/vsc.csv'
# Save to file -- answer to your question
IO.write(filename, rows.map(&:to_csv).join)
# Read from file
# rows3 = IO.read(filename).split("\n").map(&:parse_csv)
rows3 = CSV.read(filename)
rows3 == rows2 # true
rows3 == rows # false
Note: CSV loses all type information, you can use JSON to preserve basic type information, or go to verbose (but more easily human-editable) YAML to preserve all type information -- for example, if you need date type, which would become strings in CSV & JSON.
Building on #boulder_ruby's answer, this is what I'm looking for, assuming us_eco contains the CSV table as from my gist.
CSV.open('outfile.txt','wb', col_sep: "\t") do |csvfile|
csvfile << us_eco.first.keys
us_eco.each do |row|
csvfile << row.values
end
end
Updated the gist at https://gist.github.com/tamouse/4647196
Struggling with this myself. This is my take:
https://gist.github.com/2639448:
require 'csv'
class CSV
def CSV.unparse array
CSV.generate do |csv|
array.each { |i| csv << i }
end
end
end
CSV.unparse [ %w(your array), %w(goes here) ]

Append row to csv file Ruby 1.9 CSV lib

Using Ruby 1.9 and CSV lib, I can't seem to append a row. The example in the documentation opens the file, and overwrites the row. What is the correct way to append rows to the document?
Example from documentation:
require 'csv'
CSV.open("path/to/file.csv", "wb") do |csv|
csv << ["row", "of", "CSV", "data"]
csv << ["another", "row"]
# ...
end
I think you can change the open to use ab:
CSV.open("t.csv", "ab") do |csv|
I will usually use the following to write to a csv file (Or any file)
File.open("filename", 'a+') {|f| f.write("datatowrite\n)}
File.open('filename', 'a'){ |outfile|
CSV::Writer.generate(outfile) do |csv|
csv << ['c1', nil, '', '"', "\r\n", 'c2']
end
}

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