How To Create a Tk Logging Widget in Python

It’s GUI time in Python land which means I want a fully-featured GUI application built entirely from Python source. ‘Fully featured’ includes logging: I want everything I log to show up on the GUI somehow. Luckily, there’s an easy way to combine GUI widgets in Tk and the Python logging framework.

Example

Here’s the code that integrates logging into a Tk GUI:

#!/usr/bin/python

import Tkinter as tk
import logging
from time import sleep
from ScrolledText import ScrolledText
import threading


#Define a helper thread to add messages to the log 
def helperThread():
    #Sleep for 1s to allow the GUI to initialize before sending log messages
    sleep(1)
    
    t = threading.currentThread()
    while getattr(t, "do_run", True):
        logging.debug("Log message")
        sleep(5)
        
#Define a new logging handler class which inherits the logging.Handler class

class widgetLogger(logging.Handler):
    #The init function needs the widget which will hold the log messages passed to it as 
    #well as other basic information (log level, format, etc.)
    
    def __init__(self, widget,logLevel,format):
        logging.Handler.__init__(self)
        
        #Basic logging configuration
        self.setLevel(logLevel)
        self.setFormatter(logging.Formatter(format))
        self.widget = widget
        
        #The ScrolledText box must be disabled so users can't enter their own text
        self.widget.config(state='disabled')

    #This function is called when a log message is to be handled
    def emit(self, record):
        #Enable the widget to allow new text to be inserted
        self.widget.config(state='normal')
        
        # Append log message to the widget
        self.widget.insert('insert', str(self.format(record) + '\n'))
        
        #Scroll down to the bottom of the ScrolledText box to ensure the latest log message
        #is visible
        self.widget.see("end")
        
        #Re-disable the widget to prevent users from entering text
        self.widget.config(state='disabled')


class mainGui:
    def __init__(self,geometry="1000x500",title="Logging GUI"):
        #GUI Setup        
        self.root = tk.Tk()

        #Set window size
        self.root.geometry(geometry)

        #Set window title
        self.root.title(title)
        
        #Generate a ScrolledText widget to display the log
        self.logWidget = ScrolledText(self.root)
        self.logWidget.pack()

#Logging configuration
logFormatStr = '%(asctime)s - %(threadName)s - %(funcName)s  - %(levelname)-8s %(message)s'
logging.basicConfig(format=logFormatStr,level=logging.DEBUG)
        
#Instantiate the main GUI window
root = mainGui()

#Instantiate a new GUI logging handler
guiLogger = widgetLogger(root.logWidget,logging.DEBUG,format=logFormatStr)
logging.getLogger().addHandler(guiLogger)
    
threadHandle = threading.Thread(target=helperThread,args=())
threadHandle.start()
    
try:
    root.root.mainloop()
except KeyboardInterrupt:
    pass
#Remove the GUI logging handler before any more logging calls try to access the GUI
logging.getLogger().removeHandler(guiLogger)

threadHandle.do_run = False
threadHandle.join()

Resources

Stackoverflow Answer