I have a python script named "main.py" which basically uses the microphone of the user, recognizes commands and executes a task. If I say "Hello" the script will process this, answer with "Hello" and execute a command like this: print("Hello user!")

What I'm trying to do is display the output or basically the "print" from the main function into the kivy ouput_textbox. I've already asked chatgpt but it still doesn't work. The following code is from the boot.py file which starts the kivy window. The window itself works fine.

def bootEngram(self, instance):
        try:
            output_textbox = TextInput(
                readonly=True,
                background_color=(0, 0, 0, 1),
                foreground_color="#55ead4",
                font_size=14,
                font_name=fontFile,
                multiline=True
            )

            command = ["python", "D:\\silverhand\\code\\main.py"]
            process = subprocess.Popen(command, stdout=subprocess.PIPE, stderr=subprocess.PIPE, text=True, bufsize=1, universal_newlines=True)

            def update_output_text(instance, line):
                instance.text += line

            def read_output():
                for line in iter(process.stdout.readline, ''):
                    Clock.schedule_once(lambda dt: update_output_text(output_textbox, line))  # Sichere UI-Aktualisierung
                process.stdout.close()

                for err in iter(process.stderr.readline, ''):
                    Clock.schedule_once(lambda dt: update_output_text(output_textbox, f"Error: {err}"))
                process.stdout.close()
                process.stderr.close()

                process.wait()
                Clock.schedule_once(lambda dt: output_popup.dismiss())

            threading.Thread(target=read_output, daemon=True).start()
        
            popup_content = BoxLayout(orientation="vertical", spacing = 10)


            title_bar = BoxLayout(orientation="horizontal", size_hint_y=None, height=40, padding=(10, 5))

            title_label = Label(
                text="Engram",
                color="#f3e600",
                font_name=fontFile,
                font_size=20,
                bold=True,
                halign="left",
                size_hint_x = 1,
                valign = "middle"
            )

            close_button = Button(
                text="<",
                size_hint=(None, None),
                size=(30, 30),
                background_color=(0, 0, 0, 1),
                color=(1, 1, 1, 1),
                bold=True,
                size_hint_x = None
            )

            close_button.bind(on_press=lambda x: output_popup.dismiss())
            #close_button.bind(on_press=lambda x: process.stdin.write("exit\n"))

            title_bar.add_widget(title_label)

            popup_content.add_widget(output_textbox)
            popup_content.add_widget(close_button)


            output_popup = Popup(
                title="Engram",
                title_color="#f3e600",
                title_size=20,
                title_font=fontFile,
                size_hint=(0.9, 0.9),
                separator_color="#c5003c",
                #separator_height = 0,
                auto_dismiss=False,
                content=popup_content
            )

            output_popup.open()

        except Exception as e:
            print(f"Error: {e}")