Output array to CSV in Ruby

Question

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

User · Answer

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  lt  lt  i       end   end end  CSV unparse    w your array    w goes here

User · Answer

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  lt  lt  us eco first keys   us eco each do  row      csvfile  lt  lt  row values   end end   Updated the gist at https   gist github com tamouse 4647196

User · Answer

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  lt  lt  CSV generate line row    join        gt   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  lt  lt  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  lt  lt  Model column names   Model where query  each do  m      csv  lt  lt  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  amp  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  lt  lt  hsh keys  adding header row  column labels      else       csv  lt  lt  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

User · Answer

To a file   require  csv  CSV open  myfile csv    w   do  csv    csv  lt  lt    row    of    CSV    data     csv  lt  lt    another    row           end   To a string   require  csv  csv string   CSV generate do  csv    csv  lt  lt    row    of    CSV    data     csv  lt  lt    another    row           end   Here s the current documentation on CSV  http   ruby-doc org stdlib libdoc csv rdoc index html

User · Answer

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  amp  to csv  join

User · Answer

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  amp  to csv  join                1 2 3 n4 5 n         and back  as String     rows2   csv split   n   map  amp  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  amp  to csv  join     Read from file   rows3   IO read filename  split   n   map  amp  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  amp  JSON

[ruby] Output array to CSV in Ruby

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