Call a Python script from React with next routing and a node.js server

user_12922190 0
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I am working on an ethereum application that uses react, next-routing and a basic node.js server. I want to run a python script on a specific route, claimAnalysis to be specific, in order to perform some predictions. I want the script to be executed every time I visit the claimAnalysis route.

server.js

const express = require("express")();
const next = require("next");

const app = next({
    dev: process.env.NODE_ENV !== "production"
});

const routes = require("./routes");
const handler = routes.getRequestHandler(app);

app.prepare().then(() => {
    const server = express.use(handler);

    server.listen(3000, (err) => {
        if(err) throw err;
        console.log("Server ready on localhost:3000");
    });
});

routes.js

const routes = require("next-routes")();

routes
    .add("/insurance/new", "/insurance/new")
    .add("/insurance/:address", "/insurance/show")
    .add("/insurance/:address/claims", "/insurance/claims/index")
    .add("/insurance/:address/claims/new", "/insurance/claims/new")
    .add("/insurance/:address/claims/:id/claimAnalysis", "/insurance/claims/claimAnalysis");
    
module.exports = routes;

Please guide me if I can call a function from the claimAnalysis.js file that runs the python script.

ethereum next.js reactjs node.js python
2 Answers

If you're using Node 10+, you can use util.promisify to execute your python scriptwhich returns a Promise<{ stdout, stderr }> object. See an example below:

const util = require('util');
const exec = util.promisify(require('child_process').exec);

// function to execute python script
async function executeScript(path) {
  try {
    const { stdout, stderr } = await exec(`python3 ${path}`);
    console.log('stdout:', stdout);
    console.log('stderr:', stderr);
  } catch (e) {
    console.error(e); 
  }
}

Now let's use the function in your route:

app.get('/insurance/claims/claimAnalysis', async function (req, res) {
  await executeScript();
  res.send('claimAnalysis request completed');
  ...

})
user_80115440

You can use "child_process" to finish function. You can see this example:

const path = require('path')
const {spawn} = require('child_process')
/**
   * Run python myscript, pass in `-u` to not buffer console output
   * @return {ChildProcess}
*/
function runScript(){
   return spawn('python', [
      "-u",
      path.join(__dirname, 'myscript.py'),
     "--foo", "some value for foo",
   ]);
}
const subprocess = runScript()
// print output of script
subprocess.stdout.on('data', (data) => {
   console.log(`data:${data}`);
});
subprocess.stderr.on('data', (data) => {
   console.log(`error:${data}`);
});
subprocess.stderr.on('close', () => {
   console.log("Closed");
});
user_156290000
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