How do I add a row of data to specific columns? - ruby

I have a CSV named test.csv, whose headers look like this:
"Fruit","Weight","Color"
In my ruby script, I have an array that looks like this:
["Banana","Yellow"]
How do I use Ruby's csv class to put "Banana" in column "Fruit" and "Yellow" in column "Color"?

For your example:
CSV.open("path/to/file.csv", "wb") do |csv|
fruit, color = ["Banana","Yellow"]
csv << [fruit, nil, color]
end
And if you have multiple rows with the same structure:
CSV.open("path/to/file.csv", "wb") do |csv|
rows.each do |row|
# Assuming row looks like ["Banana", "Yellow"]
fruit, color = row
csv << [fruit, nil, color]
end
end
And if in your real life example your arrays have many more columns (not just two) and you want to add a few empty columns sporadically, you can use the Array#insert method:
CSV.open("path/to/file.csv", "wb") do |csv|
rows.each do |row|
# Run one line like this for every empty column you want to add
# Note that it changes the value of `row`, so if you'd like to
# keep it untouched, consider using `dup`
row.insert(1, nil)
csv << row
end
end

Related

Ruby: How to add two lines at once to a csv?

I have a list of items and a script which generates two lines of csv for each item.
May I add two lines at once to csv generator? I want something like this:
CSV.generate do |csv|
items.each do |item|
csv << rows(item)
end
end
def rows(item)
return \
['value1', 'value2', 'value2'],
['value3', 'value4', 'value5']
end
But csv << can't receive two lines at once.
Now my the best code is:
CSV.generate do |csv|
items.each do |item|
rows(item).each { |row| csv << row }
end
end
Update: Now the best code without adding two line at once looks like:
CSV.generate do |csv|
items.
flat_map(&method(:rows)).
each(&csv.method(:<<))
end
CSV.generate do |csv|
csv << items.flat_map(&method(:rows))
end
Array#push or Array#append work the same way, and can take multiple arguments. Edit: As it turns out, CSV.generate yields a CSV object which has neither of those methods.
You can also do it like this:
CSV.generate do |csv|
items.each do |item|
r = rows(item)
csv << r[0] << r[1]
end
end

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

Writing integer values to spreadsheet

I am using the following code to convert a csv to spreadsheet:
require 'spreadsheet'
require 'csv'
book = Spreadsheet::Workbook.new
sheet1 = book.create_worksheet
CSV.open("product_2014-11-19_10-41-00.csv", 'r') do |csv|
csv.each_with_index do |row, i|
sheet1.row(i).replace(row)
end
end
book.write("temp.xls")
But on doing so, the spreadsheet contains a leading quote for columns that hold integer values. Eg consider the row SGDEL,18,,,,140,0,Bib columns corresponding to 18, 140 and 0 become '18, '140, '0. Why is this so? How can I fix this?
Thanks
There is an option for CSV#open:
# vvvvvvvvvvvv
CSV.open("…", "…", { force_quotes: false }) do |csv|
Setting it to false should do the trick.

How to compare an array with the last inserted array in a csv file?

I generate arrays that I append to a file with:
require 'csv`
CSV.open(FILE_NAME, "a+") do |csv|
csv << array
end
I want to skip the insertion if the index [0] value is identical to the last inserted array's [0].
How can I read the last line/row of a csv file and compare it's values with an array that's still not inserted?
Working around some of what #Patru said:
require 'csv'
csv = CSV.open(FILE_NAME, "a+")
first_row = csv.first
csv.rewind
last_row = csv.reverse_each.first
csv << ary unless ary == first_row or ary == last_row

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) ]

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