Redirect command line results to a tkinter GUI

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).

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:

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!"