Develop Reference

How do I execute a code within a tk.Toplevel()

I'm somewhat new to python (started in Nov.) and after complete my first "program" I'm trying to built the GUI using Tkinter. I want to put the program on a Toplevel that I've created and have it run, but all Tkinter tutorials only talk about widgets and I don't know how to specify that a code should run on a specific Toplevel window. The best I can figure is to run the in the section where I define the Toplevel as shown in the example below, but that is not working.
from tkinter import *
import tkinter as tk
root=Tk()
root.geometry("500x200")
root.title('Test')
Label(root, text="Test").pack()
def test():
gen_win = Toplevel(root)
gen_win.title("Test")
gen_win.geometry("500x500")
Label(gen_win, text="Test").pack()
print(2+2)
btn_test=tk.Button(root, text="test", command=test).pack(fill=tk.X)
root.mainloop()
The example program (print(2+2)) doesn't print on the toplevel. Any ideas?

#jasonharper gave the correct answer:
"Code doesn't "run on a specific Toplevel window". It just runs, and if it happens to create a widget, or modify the contents of an existing widget, that change becomes visible as soon as your code returns to the mainloop. Label(gen_win, text=str(2+2)).pack() would be the simplest way to make your addition results visible in the window."

Tkinter not working the first time it runs with withdraw()

I am trying to make a Tkinter script to select files through Windows File Explorer. I don't need the Tkinter window to show, just the File Explorer interface.
import tkinter
from tkinter import filedialog
import os
window = tkinter.Tk()
#window.geometry("1x1")
window.withdraw()
def open_files():
files = filedialog.askopenfiles(mode='r')
global filenames
filenames = [os.path.abspath(file.name) for file in files]
window.destroy() # analysis:ignore #says "window" is undefined becasue of "del window" below
window.after(0, open_files)
window.mainloop()
del window
The first time I run this in Spyder, if window.withdraw() is not commented out, the console just shows runfile(*my_file_name*) and the code does... something... in the background, but nothing seems to actually happen. Nothing changes on-screen, but I cannot type in the console so I know the code is running.
If I open a new console tab and run the code with window.withdraw() commented out, everything works, and the Tkinter GUI is visible. If I then run this code again in the same tab, with window.withdraw() not commented out, then the code works as intended, with only the File Explorer window opening up, and the Tkinter GUI staying hidden. This is the case even if I click the "Remove all variables" button in Spyder, so as far as I understand the code is not saving any variables that allow it to run properly after the first time.
My question is, why does this code work the 2nd, 3rd, 4th, etc. time I run it, but not the first time?

I kept playing around, and changed -alpha to alpha and got this error:
TclError: wrong # args: should be "wm attributes window ?-alpha ?double?? ?-transparentcolor ?color?? ?-disabled ?bool?? ?-fullscreen ?bool?? ?-toolwindow ?bool?? ?-topmost ?bool??"
So I ended up changing window.attributes('-alpha',0) to window.attributes('-topmost',True, '-alpha',0), and this works! It brings up File Explorer on the first run without showing the Tkinter window. Thank you #Thingamabobs for your help.
My final code is:
import tkinter
from tkinter import filedialog
import os
window = tkinter.Tk()
window.attributes('-topmost',True, '-alpha',0)
filenames = [os.path.abspath(file.name) for file in filedialog.askopenfiles(mode='r')]
window.destroy()
del window

tkinter wiget.bind('<Activate>', callback) not working

I've been trying to create a message box when a button turns from disabled to active but when the button actually turns from disabled to active for some reason my callback is not even being called I've tried to get it working so for quite a bit of time now and I'm stuck.
Here is an example of the problem:
from tkinter import *
from tkinter import Tk
def disable_and_activate():
b.config(state = DISABLED)
b.config(state = ACTIVE)
def is_working(event):
print('working')
root = Tk()
b = Button (root, text = 'click me', command = disable_and_activate)
b.pack()
b.bind('<Activate>', is_working)
root.mainloop()
Console:
the button is clicked but there's nothing printed on the console

The <Activate> event is not triggered when you set the state of the button to "active". The event is triggered when the window becomes the active window.
For example, when I run your code on my OSX machine, if I click on some other application to give it focus and then I click back to the tkinter window, the event will fire when the tkinter window becomes the active window.
This is explained in the canonical tcl/tk documentation which says this:
Activate, Deactivate
These two events are sent to every sub-window of a toplevel when they change state. In addition to the focus Window, the Macintosh platform and Windows platforms have a notion of an active window (which often has but is not required to have the focus). On the Macintosh, widgets in the active window have a different appearance than widgets in deactive windows. The Activate event is sent to all the sub-windows in a toplevel when it changes from being deactive to active. Likewise, the Deactive event is sent when the window's state changes from active to deactive. There are no useful percent substitutions you would make when binding to these events.

Here the problem was just the code inside the function , It seems like you needed to call EventGenerate('<<Activate>>') I also recommend adding 2 << and 2 >>
So I rewrote the code and its now working perfectly fine:
from tkinter import *
from tkinter import Tk
import tkinter
def disable_and_activate():
b.configure(state=tkinter.DISABLED)
b.configure(state=tkinter.ACTIVE)
b.event_generate("<<Activate>>")
def is_working(event):
print('working')
root = Tk()
b = Button (root, text = 'click me', command = disable_and_activate)
b.pack()
b.bind('<<Activate>>', is_working)
root.mainloop()

Is there a way to make a custom askopenfilenames dialog window or at least edit its title bar, close button, etc in tkinter?

I'm making an app in tkinter which uses the ttk.Scale widget to show the process of an mp3 song.
I have a function that I want to add buttons with the names of which (the buttons) should be relied on filenames. Therefore I've made this example:
from tkinter import Tk, Button
from tkinter.filedialog import askopenfilenames
from tkinter.ttk import Scale
from threading import Timer
root = Tk()
slider = Scale(root, from_=0, to=100, orient='horizontal')
slider.pack()
# slider is continuously set to a bigger number so that it keeps going
def update_slider(num):
slider.set(num)
num += 1
root.after(50, update_slider, num)
update_slider(num=0)
# this function creates buttons based on the files opened
def add_buttons():
# the 'X' button of this particular window slows down execution of update_slider function
files = askopenfilenames(title='Add Buttons')
for i in list(files):
Button(root, text=i).pack()
button = Button(root, text='Browse', command=lambda: Timer(0.1, add_buttons).start())
button.pack()
root.mainloop()
The problem I'm facing is that when I open the askopenfilenames dialog box or when I press its 'X' button, my slider which is running continuously in the background gets stuck, and as a result doesn't show the process correctly.
Here is a picture where I hold down the 'X' button and the ttk.Scale stops moving:
I've tried using threading to run the add_buttons function but the behavior of the program remains the same.
Can I edit the askopenfilenames dialog box with something similar like overrideredirect(True) so that I can make my own title bar and 'X' button and the events generated not to slow down my Scale?
Replying to:
I cannot reproduce the issue in Linux, the scale keeps moving no matter what I do with the filedialog window. So this may be an OS specific issue.
I'm aware that this problem doesn't appear on Linux. I faced the same problem with the root's close button and other Toplevels' close button, but I fixed it by replacing the title bar using overrideredirect(True).
Is there anything similar I can do with this askopenfilenames window?

Python 3 tkinter: focus_force on messagebox

I'm running python 3 code in background which should show a popup window in some situations. I'm using tkinter for this:
import tkinter as tk
from tkinter import messagebox
def popup(message, title=None):
root = tk.Tk()
root.withdraw()
root.wm_attributes("-topmost", 1)
messagebox.showinfo(title, message, parent=root)
root.destroy()
popup('foo')
The ok-button in this infobox should get the focus automatically when popping up. Sadly I'm not able to do this. I tried root.focus(), but it does not help. Any ideas how to solve that? TIA
BTW: The code should be platform independent (Linux and Windows).
Edit:
Maybe I missunderstood the focus keyword and I should clarify my question:
root = tk.Tk()
root.focus_force()
root.wait_window()
When calling the code above the root window is active, even if I worked in e.g. the browser before. Is this also possible for messagebox.showinfo? Adding root.focus_force() in the popup function does not help.
Is this even possible? Or is it necessary to create my own root window? I really like the appearance of the messagebox with the icon.
Edit 2:
Here is a video: https://filebin.net/no195o9rjy3qq5c4/focus.mp4
The editor is the active window, even after the popup was shown.
In Linux I it works as expected.

You can use the default argument in the messagebox function.
default constant
Which button to make default: ABORT, RETRY, IGNORE, OK, CANCEL, YES, or NO (the constants are defined in the tkMessageBox module).
So, here is an example to highlight the "ok" button.
import tkinter as tk
from tkinter import messagebox
def popup(message, title=None):
root = tk.Tk()
root.withdraw()
messagebox.showinfo(title, message, parent=root, default = "ok")
root.destroy()
popup('foo')
Hope this helps!