如何在Python中检索tkinter ttk Scale小部件的整数值？

Question

Could anyone advise how to retrieve and update a Label widget with the value from a Scale widget in Python? Currently it shows a very large real number. I have tried to type cast the value but this only works when I print to idle. I tried slider.get() but the label is blank. Also tried int(slider.get()) which works when I print to idle.

from tkinter import *
from tkinter import ttk

root = Tk()
root.title("Playing with Scales")

mainframe = ttk.Frame(root, padding="24 24 24 24")
mainframe.grid(column=0, row=0, sticky=(N, W, E, S))

slider = IntVar()

ttk.Scale(mainframe, from_=0, to_=100, length=300,  variable=slider).grid(column=1, row=4, columnspan=5)
ttk.Label(mainframe, textvariable=slider).grid(column=1, row=0, columnspan=5)

for child in mainframe.winfo_children(): child.grid_configure(padx=5, pady=5)


root.mainloop()

Here you can see the very large real value:

Answer 1

I don't see a way to control the resolution of the Scale widget, but it's fairly easy to modify the string it produces. According to these ttk docs the Scale widget returns a float, but in my experiments it returns a string, which is slightly annoying.

Rather than setting the Label text directly from the slider variable attached to the Scale widget we can bind a command to the Scale widget that converts the string holding the Scale's current value back to a float, and then format that float with the desired number of digits; the code below displays 2 digits after the decimal point.

import tkinter as tk
from tkinter import ttk

root = tk.Tk()
root.title("Playing with Scales")

mainframe = ttk.Frame(root, padding="24 24 24 24")
mainframe.grid(column=0, row=0, sticky=('N', 'W', 'E', 'S'))

slider = tk.StringVar()
slider.set('0.00')

ttk.Scale(mainframe, from_=0, to_=100, length=300, 
    command=lambda s:slider.set('%0.2f' % float(s))).grid(column=1, row=4, columnspan=5)

ttk.Label(mainframe, textvariable=slider).grid(column=1, row=0, columnspan=5)

for child in mainframe.winfo_children(): 
    child.grid_configure(padx=5, pady=5)

root.mainloop()

If you just want the Label to display the integer value then change the initialization of slider to

slider.set('0')

and change the callback function to

lambda s:slider.set('%d' % float(s))

---

I've made a few other minor changes to your code. Primarily, I replaced the "star" import with import tkinter as tk ; the star import brings in over 130 names into your namespace, which creates a lot of unnecessary clutter, as I mentioned in this recent answer .

Answer 2

An other less complicated option and easy to use alternative is to use an instance of tkinter.Scale() class with which you can inject the resolution option to whatever value you want. The default one is the one you are looking for because its value is 1