How to Get Specific Row Value From CSV? - ruby

Question

I have a vertical CSV file that looks like this:
name,value
case,"123Case0001"
custodian,"Doe_John"
PDate,"10/30/2013"
I can read the file like this:
CSV.foreach("#{batch_File_Dir_cdata}", :quote_char => '"', :col_sep =>',', :row_sep =>:auto, :headers => true) do |record|
ev_info = record[0]
ev_val = record[1]
The problem is, I need to get a specific ev_val for just one specific ev_info. I could potentially use the row number, but foresight tells me that this could change. What will be the same is the name of information. I want to find the row with the specific information name and get that value.
When I do the foreach, it gets that value and then goes past it and leaves me with an empty variable, because it went on to the other rows.
Can anyone help?

Answer 1

You've got a lot of choices, but the easiest is to assign to a variable based on the contents, as in:
ev_info = record[0]
ev_val = record[1] if ev_info='special name'
Note, though, that you need to define whatever variable you are assigning to outside of the block as it will otherwise be created as a local variable and be inaccessible to you afterwards.
Alternatively, you can read in the entire array and then select the record you're interested in with index or select.

Answer 2

I'd do it something like:
require 'pp'
require 'csv'
ROWS_IN_RECORD = 4
data = []
File.open('test.dat', 'r') do |fi|
loop do
record = {}
ROWS_IN_RECORD.times do
row = fi.readline.parse_csv
record[row.first] = row.last
end
data << record
break if fi.eof?
end
end
pp data
Running that outputs:
[{"name"=>"value",
"case"=>"123Case0001",
"custodian"=>"Doe_John",
"PDate"=>"10/30/2013"},
{"name"=>"value_2",
"case"=>"123Case0001 2",
"custodian"=>"Doe_John 2",
"PDate"=>"10/30/2013 2"}]
It returns an array of hashes, so each hash is the record you'd normally get from CSV if the file was a normal CSV file.
There are other ways of breaking down the input file into logical groups, but this is scalable, with a minor change, to work on huge data files. For a huge file just process each record at the end of the loop instead of pushing it onto the data variable.

Answer 3

I got it to work. I original had the following:
CSV.foreach("#{batch_File_Dir_cdata}", :quote_char => '"', :col_sep =>',', :row_sep =>:auto, :headers => true) do |record|
ev_info = record[0]
c_val = record[1]
case when ev_info == "Custodian"
cust = cval
end
end
puts cust
what I needed to do was this:
CSV.foreach("#{batch_File_Dir_cdata}", :quote_char => '"', :col_sep =>',', :row_sep =>:auto, :headers => true) do |record|
ev_info = record[0]
case when ev_info == "Custodian"
c_val = record[1]
end
end
puts c_val