Redirect command line results to a tkinter GUI

Question

I have created a program that prints results on command line. (It is server and it prints log on command line.)

Now, I want to see the same result to GUI .

How can I redirect command line results to GUI?

Please, suggest a trick to easily transform console application to simple GUI.

Note that it should work on Linux and Windows.

Answer 1

To display subprocess' output in a GUI while it is still running, a portable stdlib-only solution that works on both Python 2 and 3 has to use a background thread:

#!/usr/bin/python
"""
- read output from a subprocess in a background thread
- show the output in the GUI
"""
import sys
from itertools import islice
from subprocess import Popen, PIPE
from textwrap import dedent
from threading import Thread

try:
    import Tkinter as tk
    from Queue import Queue, Empty
except ImportError:
    import tkinter as tk # Python 3
    from queue import Queue, Empty # Python 3

def iter_except(function, exception):
    """Works like builtin 2-argument `iter()`, but stops on `exception`."""
    try:
        while True:
            yield function()
    except exception:
        return

class DisplaySubprocessOutputDemo:
    def __init__(self, root):
        self.root = root

        # start dummy subprocess to generate some output
        self.process = Popen([sys.executable, "-u", "-c", dedent("""
            import itertools, time

            for i in itertools.count():
                print("%d.%d" % divmod(i, 10))
                time.sleep(0.1)
            """)], stdout=PIPE)

        # launch thread to read the subprocess output
        #   (put the subprocess output into the queue in a background thread,
        #    get output from the queue in the GUI thread.
        #    Output chain: process.readline -> queue -> label)
        q = Queue(maxsize=1024)  # limit output buffering (may stall subprocess)
        t = Thread(target=self.reader_thread, args=[q])
        t.daemon = True # close pipe if GUI process exits
        t.start()

        # show subprocess' stdout in GUI
        self.label = tk.Label(root, text="  ", font=(None, 200))
        self.label.pack(ipadx=4, padx=4, ipady=4, pady=4, fill='both')
        self.update(q) # start update loop

    def reader_thread(self, q):
        """Read subprocess output and put it into the queue."""
        try:
            with self.process.stdout as pipe:
                for line in iter(pipe.readline, b''):
                    q.put(line)
        finally:
            q.put(None)

    def update(self, q):
        """Update GUI with items from the queue."""
        for line in iter_except(q.get_nowait, Empty): # display all content
            if line is None:
                self.quit()
                return
            else:
                self.label['text'] = line # update GUI
                break # display no more than one line per 40 milliseconds
        self.root.after(40, self.update, q) # schedule next update

    def quit(self):
        self.process.kill() # exit subprocess if GUI is closed (zombie!)
        self.root.destroy()


root = tk.Tk()
app = DisplaySubprocessOutputDemo(root)
root.protocol("WM_DELETE_WINDOW", app.quit)
# center window
root.eval('tk::PlaceWindow %s center' % root.winfo_pathname(root.winfo_id()))
root.mainloop()

The essence of the solution is:

• put the subprocess output into the queue in a background thread
• get the output from the queue in the GUI thread.

i.e., call process.readline() in the background thread -> queue -> update GUI label in the main thread. Related kill-process.py (no polling -- a less portable solution that uses event_generate in a background thread).

Answer 2

You could create a script wrapper that runs your command line program as a sub process, then add the output to something like a text widget.

from tkinter import *
import subprocess as sub
p = sub.Popen('./script',stdout=sub.PIPE,stderr=sub.PIPE)
output, errors = p.communicate()

root = Tk()
text = Text(root)
text.pack()
text.insert(END, output)
root.mainloop()

where script is your program. You can obviously print the errors in a different colour, or something like that.

Answer 3

Sorry for my bad English. I actually, used a different way to print Command Prompt output into my new Automation tool. Please find those steps below.

1> Create a Bat File & redirect its output to a LOG file. Command Prompt command: tasklist /svc

2> Make read that file with Python 3.x. `processedFile = open('D:\LOG\taskLog.txt', 'r')

3> The Finale step. ttk.Label(Tab4, text=[ProcessFile.read()]).place(x=0, y=27)

**Hence please be informed that, I have not include scrollbar into this code yet.

Posting Screenshot:

Answer 4

Redirecting stdout to a write() method that updates your gui is one way to go, and probably the quickest - although running a subprocess is probably a more elegant solution.

Only redirect stderr once you're really confident it's up and working, though!

Example implimentation (gui file and test script):

test_gui.py:

from Tkinter import *
import sys
sys.path.append("/path/to/script/file/directory/")

class App(Frame):
    def run_script(self):
        sys.stdout = self
        ## sys.stderr = self
        try:
            del(sys.modules["test_script"])
        except:
            ## Yeah, it's a real ugly solution...
            pass
        import test_script
        test_script.HelloWorld()
        sys.stdout = sys.__stdout__
        ## sys.stderr = __stderr__

    def build_widgets(self):
        self.text1 = Text(self)
        self.text1.pack(side=TOP)
        self.button = Button(self)
        self.button["text"] = "Trigger script"
        self.button["command"] = self.run_script
        self.button.pack(side=TOP)

    def write(self, txt):
        self.text1.insert(INSERT, txt)

    def __init__(self, master=None):
        Frame.__init__(self, master)
        self.pack()
        self.build_widgets()

root = Tk()
app = App(master = root)
app.mainloop()

test_script.py:

print "Hello world!"

def HelloWorld():
    print "HelloWorldFromDef!"