Question

I want to write values parsed from a CSV file to a YAML file:

home_phone = row['HomePhone']
 if home_phone.length == 10  
  puts "First Name: #{row['first_Name']} - Home Phone: #{home_phone} -  Zip Code: #{zip_code}"
  elsif home_phone.length == 11 && home_phone.start_with?('1')   
  home_phone.slice!(0)
      puts "First Name: #{row['first_Name']} - Home Phone: #{home_phone} -  Zip Code: #{zip_code}"   
  else  
      puts "First Name: #{row['first_Name']} - Home Phone: #{"0000000000"} -  Zip Code: #{zip_code}"      
  end

The above code is used for printing the details row-wise. The output obtained from the code is:

First Name: Douglas - Home Phone: [phone] -  Zip Code: 50309'

'First Name: Aya - Home Phone: [phone] -  Zip Code: 90210'

'First Name: Audrey - Home Phone: 0 -  Zip Code: 05667'

How can I write these values to a YAML file?

Answer 1

If you want to convert a CSV file to YAML…

I created a file called “test.csv” which looks like:

First Name,Home Phone,Zip Code
Douglas,4252745000,50309
Aya,9995901339,90210
Audrey,0,05667

Using this code:

require 'csv'
require 'yaml'

csv = CSV.read('test.csv')
File.write('test.yaml', csv.to_yaml)
pp YAML.load_file('test.yaml')

Which generates:

---
- - First Name
  - Home Phone
  - Zip Code
- - Douglas
  - '4252745000'
  - '50309'
- - Aya
  - '9995901339'
  - '90210'
- - Audrey
  - '0'
  - '05667'

I get this output from pp showing a correct round-trip of the CSV data through YAML-land:

[["First Name", "Home Phone", "Zip Code"],
 ["Douglas", "4252745000", "50309"],
 ["Aya", "9995901339", "90210"],
 ["Audrey", "0", "05667"]]

This is just a simple solution, which loads the entire CSV file into memory. That’s not a scalable solution if you are processing files bigger than the available RAM on your system. CSV supports foreach which will let you read the file line by line, but YAML might find it difficult to write the file line-by-line because of how it generates the file; It expects a complete hash or array, but you’ll be passing it sub-arrays, which will result in a YAML file looking like:

---
- - First Name
  - Home Phone
  - Zip Code
---
- - Douglas
  - '4252745000'
  - '50309'
---
- - Aya
  - '9995901339'
  - '90210'
---
- - Audrey
  - '0'
  - '05667'

Loading that with YAML.load_file will result in:

[
    [0] [
        [0] "First Name",
        [1] "Home Phone",
        [2] "Zip Code"
    ]
]

In other words, only the first row will be returned.

The workaround is to use YAML.load_documents(File.open('test.yaml', 'r')) instead of load_file, which reassembles the parts into one array again.