Redirecting stdout to tkinter immediately (without waiting for the process to complete)

Question

I am writing a python app to take some inputs from the user and call a shell script based on these inputs.

This shell script can run for quite sometime, and I want to re

Answer 1

As p.communicate() will wait for the process to complete, so use p.poll() and p.stdout.readline() instead. Also put the process in a thread to avoid blocking the main thread:

import threading
...
class Gui(GuiApp):
    ...
    def runScript(self):
        print('started')
        p = subprocess.Popen(['./shellScript.sh'], stdout=subprocess.PIPE, bufsize=1, text=True)
        while p.poll() is None: # check whether process is still running
            msg = p.stdout.readline().strip() # read a line from the process output
            if msg:
                print(msg)
        print('finished')

    def testRun(self, event=None):
        # create a thread to run the script
        threading.Thread(target=self.runScript, daemon=True).start()