Redirect output from Python logger to tkinter widget

Question

Having spent some time on redirecting stdout and logging output to a tkinter text widget, I've decided I need some help. My code is as follows:

#!/usr/bin/env python
from Tkinter import *
import logging
from threading import Thread

class IODirector(object):
    def __init__(self,text_area):
        self.text_area = text_area

class StdoutDirector(IODirector):
    def write(self,str):
        self.text_area.insert(END,str)
    def flush(self):
        pass

class App(Frame):

    def __init__(self, master):
        self.master = master
        Frame.__init__(self,master,relief=SUNKEN,bd=2)
        self.start()

    def start(self):
        self.master.title("Test")
        self.submit = Button(self.master, text='Run', command=self.do_run, fg="red")
        self.submit.grid(row=1, column=2)
        self.text_area = Text(self.master,height=2.5,width=30,bg='light cyan')
        self.text_area.grid(row=1,column=1)

    def do_run(self):
        t = Thread(target=print_stuff)
        sys.stdout = StdoutDirector(self.text_area)
        t.start()

def print_stuff():
    logger = logging.getLogger('print_stuff')
    logger.info('This will not show')
    print 'This will show'
    print_some_other_stuff()

def print_some_other_stuff():
    logger = logging.getLogger('print_some_other_stuff')
    logger.info('This will also not show')
    print 'This will also show'

def main():    
    logger = logging.getLogger('main')
    root = Tk()
    app = App(root)
    root.mainloop() 

if __name__=='__main__':
    main()

I know that one can define a new logging handler based on a text widget but I can't get it working. The function "print_stuff" is really just a wrapper around many different functions all having their own logger set up. I need help with defining a new logging handler that is "global" so that it can be instantiated from each of the functions having their own logger. Any help is much appreciated.

Answer 1

Here's a completely revised answer that does what you want. I've tried to indicate which lines of the code in your question were change and where new line were added.

By default the built-inlogger.StreamHandlerhandler class outputs messages to sys.stderr, so to have them also redirectedsys.stdoutthe text widget requires constructing a new logger with a custom console handler set up to do that. Since you want this to apply to all loggers in the module, this setting needs to be applied to the nameless "root" logger that all other named loggers will inherit their setting from.

from Tkinter import *
import logging
from threading import Thread

class IODirector(object):
    def __init__(self, text_area):
        self.text_area = text_area

class StdoutDirector(IODirector):
    def write(self, msg):
        self.text_area.insert(END, msg)
    def flush(self):
        pass

class App(Frame):
    def __init__(self, master):
        self.master = master
        Frame.__init__(self, master, relief=SUNKEN, bd=2)
        self.start()

    def start(self):
        self.master.title("Test")
        self.submit = Button(self.master, text='Run', command=self.do_run, fg="red")
        self.submit.grid(row=1, column=2)
        self.text_area = Text(self.master, height=2.5, width=30, bg='light cyan')
        self.text_area.grid(row=1, column=1)

    def do_run(self):
        t = Thread(target=print_stuff)
        sys.stdout = StdoutDirector(self.text_area)
        # configure the nameless "root" logger to also write           # added
        # to the redirected sys.stdout                                 # added
        logger = logging.getLogger()                                   # added
        console = logging.StreamHandler(stream=sys.stdout)             # added
        logger.addHandler(console)                                     # added
        t.start()

def print_stuff():
    logger = logging.getLogger('print_stuff') # will inherit "root" logger settings
    logger.info('This will now show')                                  # changed
    print 'This will show'
    print_some_other_stuff()

def print_some_other_stuff():
    logger = logging.getLogger('print_some_other_stuff') # will inherit "root" logger settings
    logger.info('This will also now show')                             # changed
    print 'This will also show'

def main():
    logging.basicConfig(level=logging.INFO) # enable logging           # added
    root = Tk()
    app = App(root)
    root.mainloop()

if __name__=='__main__':
    main()

Answer 2

Just to make sure I understand correctly:

You want to print the logging messages both to your STDout and Tkinter text widget but the logging won't print in the standard console.

If it is indeed your problem here's how to do it.

First let's make a very simple console in Tkinter, it could be any text widget really but I'm including it for completeness:

class LogDisplay(tk.LabelFrame):
"""A simple 'console' to place at the bottom of a Tkinter window """
    def __init__(self, root, **options):
        tk.LabelFrame.__init__(self, root, **options);

        "Console Text space"
        self.console = tk.Text(self, height=10)
        self.console.pack(fill=tk.BOTH)

Now let's override the logging Handlers to redirect to a console in parameter and still automatically print to STDout:

class LoggingToGUI(logging.Handler):
""" Used to redirect logging output to the widget passed in parameters """
    def __init__(self, console):
        logging.Handler.__init__(self)

        self.console = console #Any text widget, you can use the class above or not

    def emit(self, message): # Overwrites the default handler's emit method
        formattedMessage = self.format(message)  #You can change the format here

        # Disabling states so no user can write in it
        self.console.configure(state=tk.NORMAL)
        self.console.insert(tk.END, formattedMessage) #Inserting the logger message in the widget
        self.console.configure(state=tk.DISABLED)
        self.console.see(tk.END)
        print(message) #You can just print to STDout in your overriden emit no need for black magic

Hope it helps.