Why Do I get an error when I try to get tkinter slider value?

Question

I am trying to read the value from a tkinter slider and use it by some functions as following

from tkinter import *
from tkinter import filedialog, Label
import cv2
from PIL import Image, ImageTk

panelA = None
panelB = None

def av_blur(k):
    global panelB
    dst_img = cv2.imread('result_img.jpg',0)
    dst_img = cv2.blur(dst_img,(5,5))
    k = int(k)
    dst_img = cv2.blur(dst_img, (k, k))
    ...

def av_blur(k):
    global panelB
    dst_img = cv2.imread('result_img.jpg',0)
    dst_img = cv2.blur(dst_img,(5,5))
    k = int(k)
    dst_img = cv2.blur(dst_img, (k, k))
    ...
root = Tk()
opt_frame = Frame(root)
opt_frame.pack( side=LEFT ,expand=1, fill='both')

img_frame = Frame(root)
img_frame.pack( side=RIGHT ,expand=1, fill='both')

src_frame = Frame(img_frame,background="black")
src_frame.pack( side=TOP ,expand=1, fill='both')

dst_frame = Frame(img_frame,background="white")
dst_frame.pack( side=BOTTOM ,expand=1, fill='both')
#
# Defining Blur functions
#
blur_sel = IntVar()
br_frame = Frame(opt_frame,width=200, height=100)
blur_sel = IntVar()
blur_sel = 4
blur_rad1 = Radiobutton(br_frame, text='Average Blur', value=0,variable=blur_sel,command=av_blur)
blur_rad2 = Radiobutton(br_frame, text='Gaussian Blur', value=1,variable=blur_sel,command=ga_blur)
blur_rad3 = Radiobutton(br_frame, text='Median Blur', value=2,variable=blur_sel)
blur_rad1.pack(side="left", expand=True)
blur_rad2.pack(side="left", expand=True)
blur_rad3.pack(side="left", expand=True)
br_frame.pack(anchor='w',side="top", fill=None,expand=0)
blur_slide = Scale(opt_frame, from_=1, to=32, length=600,tickinterval=4,command=av_blur,orient=HORIZONTAL)
blur_slide.pack(anchor="w", padx=10, pady=10)

root.mainloop()

The problem whenever I try to reas the slider value named k I keep getting the following error:

Exception in Tkinter callback
Traceback (most recent call last):
  File "/usr/lib/python3.6/tkinter/__init__.py", line 1705, in __call__
    return self.func(*args)
TypeError: av_blur() missing 1 required positional argument: 'k'

Simple example

I tried this simple example and still getting the same thing:

def open_file():
    ...

def blurring():
    print(scale.get())

root = Tk()
opt_frame = Frame(root)
opt_frame.pack( side=LEFT ,expand=1, fill='both')

img_frame = Frame(root)
img_frame.pack( side=RIGHT ,expand=1, fill='both')

src_frame = Frame(img_frame,background="black")
src_frame.pack( side=TOP ,expand=1, fill='both')

dst_frame = Frame(img_frame,background="white")
dst_frame.pack( side=BOTTOM ,expand=1, fill='both')
#
# Defining main window menu
#
menu = Menu(root)
new_item = Menu(menu)
new_item.add_command(label='Open File', command=open_file)
new_item.add_separator()
new_item.add_command(label='Save File')
new_item.add_separator()
new_item.add_command(label='Exit')
menu.add_cascade(label='File', menu=new_item)
root.config(menu=menu)
#
# Defining Blur functions
#
scale = Scale(opt_frame,orient='horizontal', from_=0, to=128, command=blurring)
scale.pack()
root.mainloop()

But it worked when I tried the example in here.

Answer 1

Simplifying your 2nd example you need to have an argument handled in your function that is trying to get the value of Scale.

Scale is already passing an argument so you dont need to write a lambda to manage this.

Simple do this:

import tkinter as tk


def blurring(value):
    print(value)

root = tk.Tk()
scale = tk.Scale(root, orient='horizontal', from_=0, to=128, command=blurring)
scale.pack()
root.mainloop()

Results:

Answer 2

In the command option for blur_slide, change it either:

...command = lambda: av_blue(k) # where k is the value you pass to the function

EDIT

The lambda function is used here to pass the argument k when the slider is clicked or changes position.

If k is a computed value, then the computation has to be done in a different function (placed under the command option) as:

...command = precompute

def precomute():
    # calculate k here
    av_blur(k)

or change the function defintion to:

def av_blur():
    # your code here