Python Tkinter updating a Text Widget

Question

So I am new to Tkinter, and I am trying to add a graphic interface to a little file tail program I wrote. I have got everything working from a command line perspective but I am having issue's getting the text box to update on my application when you you initially load the file or when you add a line. I see that it calls tk but doesn't update as expected. below is the code:

from sys import argv
import threading
import tkinter


class MyTkApp(threading.Thread):
    def __init__(self):
        self.root = tkinter.Tk()
        self.root.title("PyTail V 1.0")
        self.s = tkinter.StringVar()
        self.s.set('Begging Tail of File')
        self.text_window = tkinter.Text(self.root, height=20, width=80)
        self.text_window.insert(tkinter.END, self.s.get())
        self.text_window.pack()
        self.root.update()
        threading.Thread.__init__(self)


def run(self):
    self.root.mainloop()


def get_current_line_count(lines):
    lines = lines.count("\n")
    return lines


def get_file(tail_name):
    file = open(tail_name, 'r')
    lines = file.read()
    file.close()
    return lines


def print_lines(lines, begin_line, tail_app):
    split_lines = lines.split("\n")
    for num in range(begin_line, len(split_lines)-1):
        #  print(split_lines[num])
        tail_app.s.set(split_lines[num])



def correct_args(argv):
    if not len(argv) == 2:
        return False
    else:
        return True


def update_window(current_lines, tail_app):
    try:
        file_lines = get_file(argv[1])
        new_lines = get_current_line_count(file_lines)
        if new_lines > current_lines:
            print_lines(file_lines, current_lines, tail_app)
            current_lines = new_lines

    except (KeyboardInterrupt, SystemExit):
            print("Now Exiting.....")
    return current_lines


if correct_args(argv):
    file_lines = get_file(argv[1])
    current_lines = get_current_line_count(file_lines)
    app = MyTkApp()
    app.start()
    print_lines(file_lines, 0, app)
    x = True
    while x:
        current_lines = update_window(current_lines, app)
else:
    print("You must supply the name of a file")

I dont think you can use textvariable with tk.Text

Joran Beasley
– Joran Beasley

2014-12-08 21:59:25 +00:00
Commented Dec 8, 2014 at 21:59 — Joran Beasley
– Joran Beasley, Commented Dec 8, 2014 at 21:59

Bryan Oakley · Accepted Answer · 2017-01-25 20:58:44Z

So I was going about this all wrong. since Tk is even driven it's always going to go into that loop and not give me what I expected. I fixed this by starting from scratch and using the .after method. Below is my revision. Overall was a really good learning experience for python and GUI.

from sys import argv
import tkinter as tk


text = tk.Text
current_line = 0
file_lines = []
pause_status = False


def pause_updates():
    global pause_status
    if pause_status:
        pause_status = False
        root.title("Pytail v1.0 - Watching File")
    else:
        pause_status = True
        root.title("Pytail v1.0 - Paused")

 def get_current_line_count(lines):
    lines = lines.count("\n")
    return lines


def get_file(tail_name):
    file = open(tail_name, 'r')
    lines = file.read()
    file.close()
    return lines

def print_lines(begin_line):
    global text
    global file_lines
    text.config(state=tk.NORMAL)
    split_lines = file_lines.split("\n")
    for num in range(begin_line, len(split_lines)-1):
        text.insert("end", (split_lines[num])+"\n")
        text.yview(tk.END)
     text.config(state=tk.DISABLED)
     text.update()

def update_window():
    try:
        global current_line
        global file_lines
        global pause_status
        if not pause_status:
            file_lines = get_file(argv[1])
            new_lines = get_current_line_count(file_lines)
            if new_lines > current_line:
                print_lines(current_line)
                current_line = new_lines
     except (KeyboardInterrupt, SystemExit):
         print("Now Exiting.....")
     root.after(1000, update_window)

def create_interface():
    global text
    global file_lines
    frame = tk.Frame(root, background="black")
    frame.place(x=10, y=10)
    frame2 = tk.Frame(root)
    scr = tk.Scrollbar(frame)
    text = tk.Text(frame, background="black", fg="green")
    text.insert("1.0", "Beginning of Tail File" + "\n")
    scr.config(command=text.yview)
    scr.pack(side="right", fill="y", expand=False)
    text.pack(side="left", fill="both", expand=True)
    frame.pack(side=tk.TOP, fill="both", expand=True)
    frame2.pack(side="bottom", anchor="w")
    pause = tk.Button(frame2, text="Pause", command=pause_updates)
    pause.pack()
    print_lines(0)
    update_window()


def correct_args(argv):
    if not len(argv) == 2:
        return False
    else:
        return True


if correct_args(argv):
    root = tk.Tk()
    root.title("Pytail v1.0 - Watching File")
    file_lines = get_file(argv[1])
    current_line = get_current_line_count(file_lines)
    create_interface()
    root.mainloop()

Joran Beasley · Accepted Answer · 2014-12-08 22:00:58Z

-1

change self.text_window = tkinter.Text(self.root, height=20, width=80)

to self.text_window = tkinter.Label(self.root,textvariable=self.s, height=20, width=80)

then get rid of the line right after that

then you can just do self.s.set("Test New Text!")

answered Dec 8, 2014 at 22:00

Joran Beasley

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3 Comments

user3656953 Over a year ago

So I modified the line as suggested but all I see is the intial text Begging Tail of File and then the program stays stuck in the mainloop.

user3656953 Over a year ago

What I am hoping to do by the way is to print the initial text, then open the file and get the read the current lines. Each of these lines should then get printed to the Label. Once that is done I enter a loop that checks to see if more lines are in the file, if so i want to add these lines

Bryan Oakley Over a year ago

For viewing the contents of a file, a Label is absolutely the wrong widget to use. It's designed to display a single line, or just a few lines, and it isn't scrollable.

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