Introduction

Ruby is a dynamic and open source language capable of carrying out large varieties of tasks and functionalities. But, there are few things that are limited to a specific language. There are scenarios where carrying out tasks in other programming language has more incentives. These incentives may be speed, convenience, better support, large community and many more.

In this blog, we are going to discuss about a problem that is not generic but may be the only way out when in need. We are going to take a look at how to make a ruby script communicate with a python script and fetch response. It is going to be similar to sending a request into an endpoint and receiving response from it.

A gem Open3 gives us ability to access stdin, stdout, and stderr when running other programs. We can install the gem simply by gem install open3.

Ruby code

1. Lets create a ruby file named hello-ruby.rb

2. Firstly, require open3 in the file by simply writing require 'open3'

3. Then, we can use the Open3.capture3 method

• Open3.capture3 gives a string for stdin; get strings for stdout, stderr
• We should pass the path to python
  • Example: /usr/bin/python for ubuntu
• Then, the second argument should be the path to the python script
• There are no more mandatory arguments to be passed. But we can pass as much arguments as we require. These are received in the python file.
• Only strings can be passed as arguments.

4. The Open3.capture3 will return stdout, stderr and status from the call

5. The final ruby code should look like:

  stdout, stderr, status = Open3.capture3(
    '/opt/venv/bin/python',
    './hello-python-script.py',
    'this is a string_parameter required in the python file',
    'in_case, we_require_an_array_to_be_passed, convert_it_to, comma_separated, string_format',
    '244'
  )

Python code

Now, lets create a python file to receive the call and then respond as per required.

1. Create a python file named hello-python-script.py

2. Import sys in the file like import sys

3. Now, we can receive the arguments passed from the Open3 call using sys.argv

• To get 'this is a string_parameter required in the python file', use sys.argv[1] since it will receive './hello-python-script.py' in the first index
• Similarly, we can get the comma separated string using sys.argv[2] and break it into required format
• In the same way, we receive '244' in sys.argv[3]

4. Do the required stuffs in python code

5. Now, we can simply send a response using sys.stdout.write("some-string")

6. We can respond json data like json.dumps(array_data)

7. The final code should look like:

   import sys
   
   sentence_arg = sys.argv[1]
   comman_separated_arg = sys.argv[2]
   number_arg = sys.argv[3]
   
   sys.stdout.write(number_arg)
   

Notes

• The reponse number_arg is recevied as stdout value in ruby code

• In case of error, the full error message is recevied as stderr

• status receives the status from the call. In case of successful call, we can check using status.success

• Simply run ruby hello-ruby.rb in command line

Example:

The following code receives data from dummyjson. We pass arguments from the ruby code into python script and return response. Product list is printed in the console if the response is successful, else print error message.

// main.rb


require 'open3'

require 'json'


search_keyword = 'Laptop'

results_limit = 3


stdout, stderr, status = Open3.capture3(
  '/usr/bin/python3',
  './fetch-dummy-json.py',
  search_keyword,
  results_limit.to_s
)


if status.success?
  puts JSON.parse(stdout)
else
  puts stderr
end

// fetch-dummy-json.py


import json

import requests

import sys


search_keyword = sys.argv[1]

results_limit = sys.argv[2]


payload={}

headers = {}

url = "https://dummyjson.com/products/search?q=" + search_keyword + "&limit=" +
results_limit


response = requests.request("GET", url, headers=headers, data=payload)


sys.stdout.write(json.dumps(response.text))