Promise support · Issue #77 · extrabacon/python-shell · GitHub

Is it possible to have the result of a python script fired as a ES6 Promise?

any news on this?

Sorry, you will have to wrap the callbacks with a 3rd party library for now. PRs are welcome though.

See: http://bluebirdjs.com/docs/api/promisification.html

This feature would be awesome, especially for users working in React, Vue, Angular etc. Any progress or where to start?

@maziarz like extrabacon said, you can use bluebird to promisfy stuff.
A good example of this is python-bridge, a very similar project to this one.

Some relevant code from their index.js:

'use strict';

let Promise = require('bluebird');
let path = require('path');
let child_process = Promise.promisifyAll(require('child_process'));

const PYTHON_BRIDGE_SCRIPT = path.join(__dirname, 'node_python_bridge.py');

Even better: if you've updated your Node environment to one of the latest long-term-support (LTS) releases (8.x at the time of writing), then util.promisify is natively supported – you already have this tool.

From 2ality.com:

const { promisify } = require('util');

const fs = require('fs');
const readFileAsync = promisify(fs.readFile);

const filePath = process.argv[2];

readFileAsync(filePath, {encoding: 'utf8'})
  .then((text) => {
      console.log('CONTENT:', text);
  })
  .catch((err) => {
      console.log('ERROR:', err);
  });

util.promisify sounds cool but we might want to continue supporting node v7 - anyone know when v7 will be deprecated?

It's also possible to create promises manually, but it takes a bit of boilerplate - see my new checkSyntaxCode I added in as an example:

	/**
	 * checks syntax without executing code
	 * @param {string} filePath
	 * @returns {Promise} rejects w/ stderr if syntax failure
	 */
	static async checkSyntaxFile(filePath:string){

		let compileCommand = `${this.defaultPythonPath} -m py_compile ${filePath}`

		return new Promise((resolve, reject) => {
			exec(compileCommand, (error, stdout, stderr) => {
				if(error == null) resolve()
				else reject(stderr)
			})
		})	
	}

@Almenon Node 7.x, along with all odd-numbered releases, are not LTS versions: their support ends as quickly as it comes. Node 8 is the current LTS Node version, so if you have things running 7, then they should already be upgraded to 8 because your support is already up.

The original blog post for the release of 7 states that support would likely end in June 2017; since it's not a LTS version, it isn't included on Node's release schedule / EOL list. For reference, you can see the full schedule by going to the nodejs.org homepage and clicking "Long term support (LTS) schedule".

So in short: it is already deprecated.

@wosevision, ah, that's good news. Thanks for the tip. I have some work in AREPL I need to get done but I can probably get to this after that. I've earmarked the issue for v1.0.1 release :)

Here's a wrapper I use, works well enough for me.

import { resolve } from "path";
import { run } from "python-shell";

export function pythonExec(
  pythonScript: string,
  args: string[]
): Promise<string[]> {
  return new Promise((done, reject) =>
    run(
      resolve(pythonScript),
      { args, scriptPath: __dirname },
      (err, results: string[]) => (err ? reject(err) : done(results))
    )
  );
}

To be honest I'm probably not going to get to this anytime soon. I'd be happy to review a PR if someone submits it. Or if someone wants to donate to charity I can use that as motivation to get around to implementing this.

We had the same issue today, and ended up promisifying it like so:

function someFunction(date, data){
  return new Promise((resolve, reject) => {
    let result;
    let pyshell = new PythonShell('pyshell_test.py', {mode: 'text', args: [date]});
    
    pyshell.send(JSON.stringify(data['someProperty']));
    
    pyshell.on('message', function (message) {
      result = JSON.parse(message);
    });
    
    pyshell.on('stderr', function (stderr) {
      console.log(stderr);
    });
    
    pyshell.end(function (err, code, signal) {
      if (err) reject(err);
      console.log('The exit code was: ' + code);
      console.log('The exit signal was: ' + signal);
      console.log('finished');
      resolve(result);
    });
    
  });
}

@nkhil implementation worked for me but I did something more like this in a Class:

callPythonScript = () => {
	return new Promise((resolve, reject) => {
		PythonShell.run(this.pythonScriptName, this.options, (err, result) => {
			if (err) reject(err);

			resolve(result);
		});
	});
};

This is done w/ the latest version of python-shell (5.0.0).

Promise support · Issue #77 · extrabacon/python-shell · GitHub

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Promise support · Issue #77 · extrabacon/python-shell · GitHub

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Promise support #77

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damianobarbati commented on Apr 26, 2017

extrabacon commented on Apr 27, 2017

maziarz commented on Jan 16, 2018

Almenon commented on Jan 17, 2018

wosevision commented on May 1, 2018

Almenon commented on Aug 20, 2018

wosevision commented on Aug 22, 2018

Almenon commented on Aug 24, 2018

jordond commented on Sep 3, 2018

Almenon commented on Aug 24, 2019

nkhil commented on Feb 21, 2020

AlexString commented on Apr 2, 2022

Almenon commented on Feb 11, 2023

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