Parsing from a JSON file in Ruby and Extract numbers from Nested Hashes

Question

Now I am working on extracting information from a JSON file in Ruby. Then how can I extract just the numbers next to the word 'score' from the following text file? For example, I want to get 0.6748984055823062, 0.6280145725181376 on and on.

{
  "sentiment_analysis": [
    {
      "positive": [
        {
          "sentiment": "Popular",
          "topic": "games",
          "score": 0.6748984055823062,
          "original_text": "Popular games",
          "original_length": 13,
          "normalized_text": "Popular games",
          "normalized_length": 13,
          "offset": 0
        },
        {
          "sentiment": "engaging",
          "topic": "pop culture-inspired games",
          "score": 0.6280145725181376,
          "original_text": "engaging pop culture-inspired games",
          "original_length": 35,
          "normalized_text": "engaging pop culture-inspired games",
          "normalized_length": 35,
          "offset": 370
        },
     "negative": [
    {
      "sentiment": "get sucked into",
      "topic": "the idea of planning",
      "score": -0.7923352042939829,
      "original_text": "Students get sucked into the idea of planning",
      "original_length": 45,
      "normalized_text": "Students get sucked into the idea of planning",
      "normalized_length": 45,
      "offset": 342
    },
    {
      "sentiment": "be daunted",
      "topic": null,
      "score": -0.5734506634410159,
      "original_text": "initially be daunted",
      "original_length": 20,
      "normalized_text": "initially be daunted",
      "normalized_length": 20,
      "offset": 2104
    },

What I have tried is that I could read a file and set the text file to a hash variable using the JSON method.

require 'json'
json = JSON.parse(json_string)

This is based on stackoverflow.com/q/40936239/128421, in which the selected answer explains how to do it for the first element in the array. Based on that, what have you tried? You need to figure out how to iterate over an array. Please read "How to Ask" including the linked pages, along with "minimal reproducible example" and meta.stackoverflow.com/questions/261592/… — the Tin Man
– the Tin Man, Commented Dec 3, 2016 at 1:04

DexterHaxxor · Accepted Answer · 2019-05-09 11:07:19Z

82

Using the JSON class:

Importing a file:

require "json"
file = File.open "/path/to/your/file.json"
data = JSON.load file

Optionally, you can close it now:

file.close

The file looks like this:

{
  "title": "Facebook",
  "url": "https://www.facebook.com",
  "posts": [
    "lemon-car",
    "dead-memes"
  ]
}

The file is now able to be read like this:

data["title"]
=> "Facebook"
data.keys
=> ["title", "url", "posts"]
data['posts']
=> ["lemon-car", "dead-memes"]
data["url"]
=> "https://www.facebook.com"

Hope this helped!

edited May 9, 2019 at 11:07

answered Dec 3, 2016 at 8:35

DexterHaxxor

1,0167 silver badges16 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

akim Over a year ago

You should not use File.read, which loads the whole file in memory. File.open works fine with JSON.load.

webaholik Over a year ago

If this is the option you choose, don't forget to file.close!

ontek Over a year ago

You need JSON.load instead of JSON.parse, parse only takes a string, load will take a file. You also need require "json" instead of include.

Rimian · Accepted Answer · 2021-09-26 00:55:29Z

29

Parse Data from File:

data_hash = JSON.parse(File.read('file-name-to-be-read.json'))

Then just map over the data!

reviews = data_hash['sentiment_analysis'].first
reviews.map do |sentiment, reviews|
  puts "#{sentiment} #{reviews.map { |review| review['score'] }}"
end

I think this is the simplest answer.

edited Sep 26, 2021 at 0:55

Rimian

38.7k17 gold badges128 silver badges119 bronze badges

answered Mar 11, 2018 at 1:54

Blair Anderson

20.3k9 gold badges82 silver badges119 bronze badges

3 Comments

DexterHaxxor Over a year ago

yeah but then you can don't know how to read it apart from just trying it out in IRB

webaholik Over a year ago

@MichalŠtein - this answer seems quite simple, and handles closing the file (your answer doesn't) - please explain your concern with this answer?

DexterHaxxor Over a year ago

The answer does not say what to do after you load it. And I am gonna add the file closing, that's a great idea.

Arun Kumar Mohan · Accepted Answer · 2018-05-02 21:52:06Z

9

You can use Array#map to collect the reviews.

reviews = json['sentiment_analysis'][0]
positive_reviews = reviews['positive']
negative_reviews = reviews['negative']

positive_reviews.map { |review| review['score'] }
=> [0.6748984055823062, 0.6280145725181376]

negative_reviews.map { |review| review['score'] }
=> [-0.7923352042939829, -0.5734506634410159]

Hope this helps!

edited May 2, 2018 at 21:52

answered Dec 2, 2016 at 23:56

Arun Kumar Mohan

11.9k3 gold badges27 silver badges47 bronze badges

4 Comments

Sookie J Over a year ago

It greatly worked as you suggested. Thank you! Could you explain what the [0] means in json['sentiment_analysis'][0]['positive']?

Arun Kumar Mohan Over a year ago

json['sentiment_analysis'] holds an array of objects and the data you're looking for is present in the first index. So, you use [0] to index into the object and then parse the "positives" object. Does this make sense?

Sookie J Over a year ago

Ok I see. Then could you take a look at the text file above again? I added "negatives" more to the text. In this case, should I use json['sentiment_analysis'][0]['negative'] or json['sentiment_analysis'][1]['negative']?

Arun Kumar Mohan Over a year ago

@SookieJ Updated the answer. Have a look and let me know if it helps.

Collectives™ on Stack Overflow

Parsing from a JSON file in Ruby and Extract numbers from Nested Hashes

3 Answers 3

3 Comments

3 Comments

4 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

3 Comments

3 Comments

4 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related