remote laboratory

The remote-lab framework of the pocket science lab enables users to access their devices remotely via the internet. Its design involves an API server built with Python-Flask and a webapp that uses EmberJS. This post is the latest in a series of blog posts which have explored and elaborated various aspect of the remote-lab such as designing the API server and testing with Postman, remote execution of function strings, automatic deployment on various domains etc. It also supports creating and submitting python scripts which will be run on the remote server, and the console output relayed to the webapp. In this post, we shall take a look at how we can extend the functionality by providing support for object oriented code in user submitted scripts. Let’s take an example of a Python script where the user wishes to create a button which when clicked will read a voltage via the API server, and display the value to the remote user. Clearly, an interpreter that only provides the console output is not enough for this task. We need the interpreter to generate an app structure that also includes callbacks for widgets such as buttons, and JSON objects are an obvious choice for relaying such a structure to the webapp. In a nutshell, we had earlier created an API method that could execute a python script and return a string output, and now we will modify this method to return a JSON encoded structure which will be parsed by the webapp in order to display an output. Let’s elaborate this with an example : Example.py print ('testing') print ('testing some changes..... ') print_('highlighted print statement')   JSON returned by the API [localhost:8000/runScriptById] , for the above script: {"Date": "Tue, 01 Aug 2017 21:39:12 GMT", "Filename": "example.py", "Id": 4, "result": [ {"name": "print", "type": "span", "value": "('testing',)"}, {"name": "print", "type": "span", "value": "('testing some changes..... ',)"}, {"class": "row well", "name": "print", "type": "span", "value": "highlighted print statement"} ], "status": true} Screenshot of the EmberJS webapp showing the output rendered with the above JSON Adding Support for Widgets In the previous section, we laid the groundwork for a flexible platform. Instead of returning a string, the webapp accepts a JSON object and parses it. We shall now add support for a clickable button which can be associated with a valid PSLab function. An elementary JS twiddle has been made by Niranjan Rajendran which will help newbies to understand how to render dynamic templates via JSON objects retrieved from APIs. The twiddle uses two API endpoints; one to retrieve the compiled JSON output, and another to act as a voltmeter method which returns a voltage value. To understand how this works in pslab-remote, consider a one line script called button.py: button('get voltage',"get_voltage('CH1')") The objective is to create a button with the text ‘get voltage’ on it , and which when clicked will run the command ‘get_voltage(‘CH1’)’ on the API server, and display the result. When this script is run on the API server, it returns…