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) ]
Related
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
I have the following array and am struggling to format it for my needs.
consolidated = [
{:name=>"Bob", :details=>{"work"=>"Carpenter", "age"=>"26", "Experience"=>"6"} },
{:name=>"Colin", :details=>{"work"=>"painting", "age"=>"20", "Experience"=>"4"} }
]
I am trying to format it as below:
Bob work Carpenter
age 26
Experience 6
Colin work painting
age 20
Experience 4
I tried the following:
require 'csv'
CSV.open("output.csv", "wb") do |csv|
csv << ["name", "nature", "details"]
consolidated.each do |val|
csv << [val[:name], val[:details]]
end
end
#=> [{:name=>"Bob", :details=>{"work"=>"Carpenter", "age"=>"26", "Experience"=>"6"}},
# {:name=>"Colin", :details=>{"work"=>"painting", "age"=>"20", "Experience"=>"4"}}]
but it prints the following
name nature details
Bob "work"=>"Carpenter", "age"=>"26", "Experience"=>"6"
Colin "work"=>"painting", "age"=>"20", "Experience"=>"4"
I'm not exactly sure how to iterate hash of hash from the 1st loop only to get the expected format.
Thanks.
Here's something to get you started:
require 'csv'
data = [
{:name => "Bob", :details=>{"work"=>"Carpenter", "age"=>"26", "Experience"=>"6"}},
{:name => "Colin", :details=>{"work"=>"painting", "age"=>"20", "Experience"=>"4"}}
]
str = CSV.generate do |csv|
data.each do |datum|
datum[:details].each do |detail_key, detail_value|
csv << [datum[:name], detail_key, detail_value]
end
end
end
puts str
# >> Bob,work,Carpenter
# >> Bob,age,26
# >> Bob,Experience,6
# >> Colin,work,painting
# >> Colin,age,20
# >> Colin,Experience,4
Simply iterate all details and emit a new row for each key-value pair there, adding a name of a person.
This will get you almost what you need. Missing only blank rows between sections and person's name is duplicated on each line. It'll be your homework to find out how to add those improvements.
I don't know about CSV generation (so, assuming it works as you have written), you can iterate on your object this way:
consolidated = [{:name => "Bob", :details=>{"work"=>"Carpenter", "age"=>"26", "Experience"=>"6"}}, {:name => "Colin", :details=> {"work"=>"painting", "age"=>"20", "Experience"=>"4"}}]
CSV.open("output.csv", "wb") do |csv|
csv << ["name", "nature", "details"]
consolidated.each do |val|
details = val[:details]
nature_1 = details.keys.first
detail_1 = details.delete(nature_1)
csv << [val[:name], nature_1, detail_1]
details.each do |k, v|
csv << [nil, k, v]
end
end
end
Note: This will corrupt your original data array consolidated. So, if you want to preserve it, dup it first. Or modify the logic to not delete the first key-value from val[:details].
You need to iterate the embedded hash by each_pair iterator.
Something like this:
data = {:name => "Bob", :details=>{"work"=>"Carpenter", "age"=>"26", "Experience"=>"6"}}
CSV.open("output.csv", "wb") do |csv|
csv << ["name", "nature", "details"]
data.each do |val|
csv << [ val[:name], val[:details]['work'] ]
data[:details].each_pair do |key, value]
# here we have to drop the first pair because i've used it earlier
next if key == 'work'
csv << [ "", key, value ]
end
end
end
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
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
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
}