return value from python-shell as response

Question

I'm using python shell to run python on nodeJS. I need to return python shell out put as the response. but when i try to send the response it shows an error

Can't set headers after they are sent.

here is my code

app.post('/therun', (req, res)=>{

    var pyshell = new PythonShell('hello.py');

    pyshell.on('message', function (message) {

       console.log(message); //value is correct
       res.send(message); //error here

      });

       res.send(message); //if i use here message undefined


});

How to slove this?

Answer 1

    app.post('/therun', (req, res)=>{

    var pyshell = new PythonShell('hello.py');
    var test={};

    pyshell.on('message', function (message) {

       console.log(message); //value is correct
       //res.send(message); //error here
      test=message;

      });
       console.log(test);
       res.send(message); //if i use here message undefined


});

Can you tell me the response on your console for the value of test ?

Answer 2

Instead of sending it as,

res.send(message); //error here

Can you please try sending the same with a status code given below?

res.status(200).json({
  "message":message
})

Hope this helps!

Answer 3

You forgot to close the python shell (after pyshell.on()):

pyshell.end(function (err) {
  if (err) throw err;
});