Tom Cupis Tom Cupis - 7 months ago 13
Python Question

Scale function not outputting number to variable?

So for some reason the scale function in tkinter doesn't want to output the number on the scale. All i receive is either 0.0 or nothing. It seems to be to do with the GUI and calling functions through the GUI. Written and run in python 3.4.

from tkinter import *
from tkinter import ttk
from tkinter import messagebox

iterations=30

def settings():
global itervar, iterscale
sGui = Tk()
itervar = DoubleVar()

iterscale = Scale(sGui, orient="horizontal", from_=1, to=1000, variable=itervar)
iterscale.pack()

iterbutton = Button(sGui, text="Save Settings", command=saveSettings)
iterbutton.pack()

sGui.mainloop()

def saveSettings():
global iterations
iterations = itervar.get()
print(iterations)

def doNothing():
pass

def main():
global root, version
root= Tk()

menu = Menu(root)
root.config(menu=menu)

fileMenu = Menu(menu)
menu.add_cascade(label="File", menu=fileMenu)
fileMenu.add_command(label="Quit", command=quit)

benchmarkMenu = Menu(menu)
menu.add_cascade(label="Benchmark", menu=benchmarkMenu)
benchmarkMenu.add_command(label="Run [All]", command=doNothing)
benchmarkMenu.add_separator()
benchmarkMenu.add_command(label="Settings", command=settings)

root.mainloop()

#Main
main()


I have tried the functions
settings
and
saveSettings
on their own and they work fine, but when i call it through the GUI it doesn't seem to work.

Any ideas on the problem, my only solution would be have the
settings
function and
saveSettings
function in a different file and then run that file externally with
os.startfile("etc...")

Answer

Minimal fix: change this

itervar = DoubleVar()

to this:

itervar = DoubleVar(sGui)

Because you have two root applications root and sGui are both instances of Tk the implied parent widget for itervar is the first one created, being root so tkinter gets confused when you specify it as the variable for a completely different application.

Or you can phase out the variable all together by using .geting the scale directly:

iterations = iterscale.get()

But I would recommend using a Toplevel instance to keep the windows a part of the same program:

sGui = Toplevel(root)
...
#sGui.mainloop() #no longer need this
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