How to Save a Hash into a CSV

How to save a hash into a CSV

Try this:

require 'csv'
h = { 'dog' => 'canine', 'cat' => 'feline', 'donkey' => 'asinine' }
CSV.open("data.csv", "wb") {|csv| h.to_a.each {|elem| csv << elem} }

Will result:

1.9.2-p290:~$ cat data.csv 
dog,canine
cat,feline
donkey,asinine

(Ruby) How to convert a nested hash into a csv file

I would do something like this:

require 'csv'

CSV.open('the_file.csv', 'w') do |csv|
  hash.each do |id, attributes|    
    csv << [id, *attributes.values_at(:price, :brand)]
  end
end

How to add an array of hashes into a csv file?

You can append to an existing file by using mode: 'a': (see open modes)

File.write("#{file_name}.csv", s, mode: 'a')

To write the headers only on the first run, you could check whether the file exists. In addition, you should use a fixed header and fetch the hash values in that specific order, e.g.:

CSV.generate do |csv|
  csv << %w[Name Age Country] unless File.exist?("#{file_name}.csv")

  hash.each do |x|
    csv << x.values_at(:Name, :Age, :Country)
  end
end

File.write("#{file_name}.csv", s, mode: 'a')

There's also CSV.open which creates the file for you:

CSV.open("#{file_name}.csv", 'a') do |csv|
  csv << %w[Name Age Country] if csv.stat.zero?

  hash.each do |x|
    csv << x.values_at(:Name, :Age, :Country)
  end
end

Since the file will always exist when the block gets executed, the header check needs to be changed: csv.stat returns the file's File::Stat and zero? determines whether the file is empty.

How to save hash values into a CSV

The join method that @joelparkerhenderson talks about just takes the two array value and joins them togheter.

You can use flatten to separate and create a new array like this:

# Open the CSV for writing
CSV.open("info.csv", "wb") do |csv|
  # Write the entire row all at once
  csv <<  @infodata.values.flatten
end 

Read more at: http://www.ruby-doc.org/core-1.9.3/Hash.html#method-i-flatten

convert array of hashes to csv file

Try this:

CSV.open("data.csv", "wb") do |csv|
  @data.each do |hash|
    csv << hash.values
  end
end

If you want the first line of the CSV to contain the keys of the hash (a header row), simply do:

CSV.open("data.csv", "wb") do |csv|
  csv << @data.first.keys # adds the attributes name on the first line
  @data.each do |hash|
    csv << hash.values
  end
end

---

Please read the comment of @cgenco below: He wrote a monkey patch for the Array class.

Creating a CSV from a hash

You need to define this method as an instance method of the class Array.

class Array
  def to_csv(csv_filename="hash.csv")
    require 'csv'
    # Get all unique keys into an array:
    keys = self.flat_map(&:keys).uniq
    CSV.open(csv_filename, "wb") do |csv|
      csv << keys
      self.each do |hash|
        # fetch values at keys location, inserting null if not found.
        csv << hash.values_at(*keys)
      end
    end   
  end
end

[{ :a=>1, :b=>2 }, { :c=>3 }].to_csv
  #=> [{:a=>1, :b=>2}, {:c=>3}] 

Let's see what was written.

CSV.read("hash.csv")
  #=> [["a", "b", "c"], ["1", "2", nil], [nil, nil, "3"]] 

I infer this is an array method from the code fragment

self.flat_map(&:keys)

As the mapping is to keys, it suggests that the reiceiver is an array of hashes.(That expression could have been written flat_map(&:keys).)

This method does not appear to meet your requirements.

You could save the keys and values thusly:

CSV.open("hash.csv", "wb") do |csv|
  arr.each do |h|
    csv << h
  end
end
  #=> [["a", "b", "c"], [1, 2, 3], [4, 5, 6]]

CSV.read("hash.csv")
  #=> [["a", "b", "c"], [1, 2, 3], [4, 5, 6]]

How could i save all the hashes generated from jpg images into a csv file and not only the last one?

Here, you're overwriting your list_rows variable for every step in the loop. You should append to the list instead, and then write the content of the list to your csv.

import imagehash
from PIL import Image
import glob
import numpy as np

image_list = []
list_rows = []

for filename in glob.glob('/home/folder/*.jpg'):
    im = Image.open(filename)
    image_list.append(im)
    img_hash = imagehash.average_hash(im)
    print(img_hash)
    list_rows.append([img_hash])

np.savetxt("numpy_test.csv", list_rows, delimiter=",", fmt='% s')

PS: Try not to override builtin (like hash) that may be dangerous !

Save hash in the csv ruby

CSV.open("users.csv", "a") {|csv|
  csv << users.values
}

I think, you need this. If users hash will contains other data - csv will take it to

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