There are soo many inherent problems with csv, 1) your columns can't have commas, so you have to encapsulate them with quotes "", and then once you encapsulate them with quotes, you have to already escape the quotes within a sentence by using \"
What is the easiest way to parse a csv file? I reverted to doing semi-colon separated files but those are troublesome when working in excel, so now i'm back to csv files.
Have you tried http://ruby-doc.org/stdlib-1.9.2/libdoc/csv/rdoc/CSV.html.
You can also look at http://fastercsv.rubyforge.org/
Check out Faster CSV from James Edward Gray II.
"FasterCSV is CSV, but faster, smaller, and cleaner."
Here is a rough example using CSV in ruby:
class DataLoader
require 'csv'
def self.import_csv
Dir.glob("/imports/*.csv").each do |csv_file|
csv = CSV.open(csv_file, {:col_sep => ",", :headers => true, :return_headers => false, :quote_char => '"'})
#data_table = csv.read
#data_table.each do |data_row|
field_one = data_row.first[0]
field_two = data_row.first[1]
#do some work
end
end
end
Related
I have some data I was writing from one CSV to another CSV because I need to do some data manipulation.
I noticed the CSV library has some default converters that are taking my values that look like dates and parsing those into new date strings.
I was wondering if I could remove all converters? I tried using my custom converter, but no matter what I do it seems that the dates keep getting parsed.
Here is my code simplified:
require 'csv'
CSV::Converters[:my_converter] = lambda do |value|
value
end
CSV.open('new-data.csv', 'w') do |csv|
data = CSV.read('original-data.csv', :converters => [:my_converter]).each do |row|
csv << row
end
end
The value 9/30/14 0:00 is getting changed to 9/30/2014 0:00, for example.
Are you sure that your CSV file doesn't actually contain the 4-digit year? Try looking at puts File.read('original-data.csv')
When I tried this on Ruby 2.1.8, it didn't change the value
require 'csv'
my_csv_data = 'hello,"9/30/14 0:00",world'
CSV.new(my_csv_data).each do |row|
puts row.inspect # prints ["hello", "9/30/14 0:00", "world"], as expected
end
CSV files are not parsed and converted into objects, the data in the fields is returned as a string. Always. This behavior is different than YAML or JSON, which do convert back to their base types.
Consider this:
require 'csv'
CSV.parse("1,10/1/14,foo") # => [["1", "10/1/14", "foo"]]
All values are strings.
csv = ["foo", 'bar', 1, Date.new(2014, 10, 1)].to_csv # => "foo,bar,1,2014-10-01\n"
Converting an array containing native Ruby objects results in a string of comma-delimited values.
CSV.parse(csv) # => [["foo", "bar", "1", "2014-10-01"]]
Reparsing that string returns the string versions but doesn't attempt to return them to their original types as CSV doesn't have a way of knowing what those were. The developer (you) has to know and do that.
The end-result of all that is that CSV won't change a year from '14' to '2014'. It doesn't know that it's a date, and, because it's not CSV's place to convert to objects, it only splits the fields appropriately and passes the information on to be massaged by the developer.
CSV.open(name, "r").each do |row|
puts row
end
And I get the following error:
CSV::MalformedCSVError Unquoted fields do not allow \r or \n
The name of the file is a .txt tab-delimited file. I made it specifically. I have a .csv file, I went to excel, and saved the file as .txt tab delimited. So it is tab delimited.
Shouldn't CSV.open be able to read tab-delimited files?
Try specifying the field delimiter like this:
CSV.open("name", "r", { :col_sep => "\t" }).each do |row|
puts row
end
And remember to require 'csv' and read the DOCS
By default CSV uses the comma as separator, this comes from the fact that CSV stands for 'Comma Separated Values'.
If you want a different separator (in this case tabs) you need to make it explicit.
Example:
p CSV.new("aaa\tbbb\tccc\nddd\teee", col_sep: "\t").read
Relevant documentation: http://ruby-doc.org/stdlib-2.1.0/libdoc/csv/rdoc/CSV.html#new
as an alternative to CSV, you can also use smarter_csv like this:
require 'smarter_csv'
data = SmarterCSV.process(filename, col_sep: "\t")
If you use smarter_csv >= 1.4.2, you can also do this:
require 'smarter_csv'
data = SmarterCSV.process(filename, col_sep: :auto)
SmarterCSV will return an array of hashes, and can do batch processing
I'm trying to join CSV files containing stock indexes with Ruby, and having a surprisingly hard time understanding the documentation out there. It's late, and I could use a friend, so go easy on me:
I have several files, with identical headers:
["Date", "Open", "High", "Low", "Close", "Volume"]
I would like my ruby script to read each "Date" column, and write to a new CSV compiling an all encompassing date range from the earliest date to the latest.
Bonus:
Ideally, I would like to add all of the other column data ("Open", "High", etc.) into this new CSV file, split by a column simply containing the following CSV's filename for reference.
Thanks for any consideration given to this. What I'd really like to do is sit down with a Ruby sensei to help me make sense of the documentation. How can I use the CSV.read() or CSV.foreach() do |x| methods to create arrays / hashes to perform upon?
(Theoretical and intelligent responses welcomed)
hypothetical:
CSV.read("data/DOW.csv") do |output|
puts output
end
returns:
[["Date", "Open", "High", "Low", "Close", "Volume"], ["2014-07-14", "71.35", "71.52", "70.82", "71.28", "823063.0"], ["2014-07-15", "71.32", "71.76", "71.0", "71.28", "813861.0"], ["2014-07-16", "71.34", "71.58", "70.68", "71.02", "843347.0"], ["2014-07-17", "70.54", "71.46", "70.54", "71.13", "1303839.0"], ["2014-07-18", "71.46", "72.95", "71.09", "72.46", "1375922.0"], ["2014-07-21", "72.21", "73.46", "71.88", "73.38", "1603854.0"], ["2014-07-22", "73.46", "74.76", "73.46", "74.57", "1335305.0"], ["2014-07-23", "74.54", "75.1", "73.77", "74.88", "1834953.0"]]
How can I identify rows, columns, etc? I'm looking for methods or ways to transform this array into hashes etc. Honestly, an overarching theoretical approach would suit my needs.
I've been playing with Ruby and CSV most of this day, I might be able to help (even though I am beginner myself) but I don't understand what do you want as output (little example would help).
This example would load only columns "Date", "High" and "Volume" into "my_array".
my_array = []
CSV.foreach("data.csv") do |row|
my_array.push([row[0], row[2], row[5]])
end
If you want every column try:
my_array = []
CSV.foreach("data.csv") do |row|
my_array.push(row)
end
If you want to access element of array inside array:
puts my_array[0][0].inspect #=> "Date"
puts my_array[1][0].inspect #=> "2014-07-14"
When you finally get what you want as output, if you are on Windows you can do this from command prompt to save it:
my_file.rb > output_in_text_form.txt
You can do something like this:
#!/usr/bin/env ruby
require 'csv'
input = ARGV.shift
output = ARGV.shift
File.open(output, 'w') do |o|
csv_string = File.read(input)
CSV.parse(csv_string).each do |r|
# r is an array of columns. Do something with it.
...
# Generate string version.
new_csv_row = CSV.generate_line(r, {:force_quotes => true})
# Write to file
o.puts new_csv_row
end
end
Using files is optional. You can use shell redirection and directly read from STDIN and/or directly write to STDOUT.
I have a CSV file that looks like this:
Jenny, jenny#example.com ,
Ricky, ricky#example.com ,
Josefina josefina#example.com ,
I'm trying to get this output:
users_array = [
['Jenny', 'jenny#example.com'], ['Ricky', 'ricky#example.com'], ['Josefina', 'josefina#example.com']
]
I've tried this:
users_array = Array.new
file = File.new('csv_file.csv', 'r')
file.each_line("\n") do |row|
puts row + "\n"
columns = row.split(",")
users_array.push columns
puts users_array
end
Unfortunately, in Terminal, this returns:
Jenny
jenny#example.com
Ricky
ricky#example.com
Josefina
josefina#example.com
Which I don't think will work for this:
users_array.each_with_index do |user|
add_page.form_with(:id => 'new_user') do |f|
f.field_with(:id => "user_email").value = user[0]
f.field_with(:id => "user_name").value = user[1]
end.click_button
end
What do I need to change? Or is there a better way to solve this problem?
Ruby's standard library has a CSV class with a similar api to File but contains a number of useful methods for working with tabular data. To get the output you want, all you need to do is this:
require 'csv'
users_array = CSV.read('csv_file.csv')
PS - I think you are getting the output you expected with your file parsing as well, but maybe you're thrown off by how it is printing to the terminal. puts behaves differently with arrays, printing each member object on a new line instead of as a single array. If you want to view it as an array, use puts my_array.inspect.
Assuming that your CSV file actually has a comma between the name and email address on the third line:
require 'csv'
users_array = []
CSV.foreach('csv_file.csv') do |row|
users_array.push row.delete_if(&:nil?).map(&:strip)
end
users_array
# => [["Jenny", "jenny#example.com"],
# ["Ricky", "ricky#example.com"],
# ["Josefina", "josefina#example.com"]]
There may be a simpler way, but what I'm doing there is discarding the nil field created by the trailing comma and stripping the spaces around the email addresses.
I would like to parse a CSV file so that each row is treated like an object with the header-row being the names of the attributes in the object. I could write this, but I'm sure its already out there.
Here is my CSV input:
"foo","bar","baz"
1,2,3
"blah",7,"blam"
4,5,6
The code would look something like this:
CSV.open('my_file.csv','r') do |csv_obj|
puts csv_obj.foo #prints 1 the 1st time, "blah" 2nd time, etc
puts csv.bar #prints 2 the first time, 7 the 2nd time, etc
end
With Ruby's CSV module I believe I can only access the fields by index. I think the above code would be a bit more readable. Any ideas?
Using Ruby 1.9 and above, you can get a an indexable object:
CSV.foreach('my_file.csv', :headers => true) do |row|
puts row['foo'] # prints 1 the 1st time, "blah" 2nd time, etc
puts row['bar'] # prints 2 the first time, 7 the 2nd time, etc
end
It's not dot syntax but it is much nicer to work with than numeric indexes.
As an aside, for Ruby 1.8.x FasterCSV is what you need to use the above syntax.
Here is an example of the symbolic syntax using Ruby 1.9. In the examples below, the code reads a CSV file named data.csv from Rails db directory.
:headers => true treats the first row as a header instead of a data row. :header_converters => :symbolize parameter then converts each cell in the header row into Ruby symbol.
CSV.foreach("#{Rails.root}/db/data.csv", {:headers => true, :header_converters => :symbol}) do |row|
puts "#{row[:foo]},#{row[:bar]},#{row[:baz]}"
end
In Ruby 1.8:
require 'fastercsv'
CSV.foreach("#{Rails.root}/db/data.csv", {:headers => true, :header_converters => :symbol}) do |row|
puts "#{row[:foo]},#{row[:bar]},#{row[:baz]}"
end
Based on the CSV provided by the Poul (the StackOverflow asker), the output from the example code above will be:
1,2,3
blah,7,blam
4,5,6
Depending on the characters used in the headers of the CSV file, it may be necessary to output the headers in order to see how CSV (FasterCSV) converted the string headers to symbols. You can output the array of headers from within the CSV.foreach.
row.headers
Easy to get a hash in Ruby 2.3:
CSV.foreach('my_file.csv', headers: true, header_converters: :symbol) do |row|
puts row.to_h[:foo]
puts row.to_h[:bar]
end
Although I am pretty late to the discussion, a few months ago I started a "CSV to object mapper" at https://github.com/vicentereig/virgola.
Given your CSV contents, mapping them to an array of FooBar objects is pretty straightforward:
"foo","bar","baz"
1,2,3
"blah",7,"blam"
4,5,6
require 'virgola'
class FooBar
include Virgola
attribute :foo
attribute :bar
attribute :baz
end
csv = <<CSV
"foo","bar","baz"
1,2,3
"blah",7,"blam"
4,5,6
CSV
foo_bars = FooBar.parse(csv).all
foo_bars.each { |foo_bar| puts foo_bar.foo, foo_bar.bar, foo_bar.baz }
Since I hit this question with some frequency:
array_of_hashmaps = CSV.read("path/to/file.csv", headers: true)
puts array_of_hashmaps.first["foo"] # 1
This is the non-block version, when you want to slurp the whole file.