Use node exec to access a function in a python file

Question

I am new to node's child_process and I am trying to execute python and get its results back to node

I want to use exec, not to execute a simple command but to access a python file and execute it

Say my python.py is

try :
    import anotherPythonFile
    print('hello2')
    # anotherPythonFile.names().getNames()  
except Exception as e :
    print(e)

I try to test this and have hello2 returned ,but I get nothing

exec('D:\prjt\test\python.py', (er, stdout, stderr)=>{
  console.log('exec test', stdout);      
})

If this worked I would uncomment and execute anotherPythonFile.names().getNames()

What is the error here?

Also, can I access the anotherPythonFile directly and somehow set the function I want to execute ? I want to do (example)

exec('D:\prjt\test\anotherPythonFile.py.names().getNames()', (er, stdout, stderr)=>{
  console.log('exec test', stdout);      
})

Is this possible?

Thank you

Telmo Trooper · Accepted Answer · 2020-07-17 14:23:05Z

2

Here's an example of running a Python script from Node.js and reading its output:

hello.py

print("Hello from Python!")

main.js

const { spawn } = require('child_process');

const py = spawn('python3', ['/home/telmo/hello.py'])

py.stdout.on('data', (data) => {
  console.log(`${data}`)
});

Running node main.js returns:

Hello from Python!

Alternatives

You can also use execFile instead of spawn:

const { execFile } = require('child_process');

const py = execFile('python3', ['/home/telmo/hello.py'], (error, stdout, stderr) => {
  if (error || stderr) {
    // Handle error.
  } else {
    console.log(stdout)
  }
})

Or exec:

const { exec } = require('child_process');

const py = exec('python3 /home/telmo/hello.py', (error, stdout, stderr) => {
  if (error || stderr) {
    // Handle error.
  } else {
    console.log(stdout)
  }
})

edited Jul 17, 2020 at 14:23

answered Jul 17, 2020 at 14:03

Telmo Trooper

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5 Comments

codebot Over a year ago

Hi there. Yes, I also know about spawn, is very flexible, but I am experimenting with exec and I was wondering if I could use exec for python files. There is a big python+node project coming up and I want to research all the options first. So exec is not a choice for python files, only spawn ? Thank you

Telmo Trooper Over a year ago

@codebot Okay, I wrote two more examples with execFile and exec to give you some options over spawn.

Telmo Trooper Over a year ago

You might want to turn the exec into a promise so you can await for it. Would you like an example of that?

codebot Over a year ago

Thanks for the tips. One last thing, is possible to define input arguments and/or a specific function in exec ? Something like exec('python3 /home/telmo/hello.py aPythonFunctionToExecute argumentOne argumentTwo' Thanks

Telmo Trooper Over a year ago

I think you'd have to use execFile or spawn for that. At least that's what it looks like in the docs.

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