i get always a 0 as a returned value, can anyone help me to extract that value and use it for further calculations ,and thanks

Question

this is the code , i get always a 0 as a returned value, can anyone help me to extract that value and use it for further calculations , i'm new in python espessially software i just need your help and ill be gratefull , thank you very much

from tkinter import *
import re
from tkinter import messagebox
from tkinter import filedialog


class Window(Frame):
    def __init__(self, master=None):
        Frame.__init__(self, master)   
        self.master = master
        self.init_window()
    def init_window(self):
     self.master.title("gcode Data")
     self.pack(fill=BOTH, expand=1)
     menu = Menu(self.master)
     self.master.config(menu=menu)
     file = Menu(menu)
     file.add_command(label="Exit", command=self.client_exit)
     menu.add_cascade(label="File", menu=file)
     quitButton = Button(self, text="Load GCODE",command=self.read_gcode)
     quitButton.place(x=60, y=50)

   
    def get_filament_value(self, fileName):
        with open(fileName, 'r') as f_gcode:
            data = f_gcode.read()
            re_value = re.search('filament used = .*? \(([0-9.]+)', data)

            if re_value:
                value = float(re_value.group(1))
                print('filament value is {}'.format(value))
            
            else:
                  value = 0.0
                  print('filament not found in {}'.format(fileName))
        return value

    def read_gcode(self):
        root.fileName = filedialog.askopenfilename(filetypes = (("GCODE files", "*.gcode"), ("All files", "*.*")))
        self.value = self.get_filament_value(root.fileName)

    def client_exit(self):
        exit()
root = Tk()
root.geometry("220x300")
app = Window(root)
root.mainloop()