Decimal Button in tkinter

Question

Hii people so I'm trying to implement a decimal button into a calculator I'm trying to make using tkinter. The decimal button works but it does not consider anything after the decimal when doing the calculations and it keeps the most recent decimal after I hit the equal buttom. and I have no idea why. This is my code right now:

from tkinter import *

root = Tk()
root.title("Calculator")

e = Entry(root, width=35, borderwidth=5)
e.grid(row=0, column=0, columnspan=4, padx=10, pady=10)

def button_press(number):
    current = e.get()
    e.delete(0, END)
    e.insert(0, str(current) + str(number))

def button_clear():
    e.delete(0, END)

def button_equal():
    second_number = e.get()
    e.delete(0, END)

    if math == "addition":
        e.insert(0, f_num + float(second_number))
        
    if math == "subtraction":
        e.insert(0, f_num - float(second_number))
        
    if math == "multiplication":
        e.insert(0, f_num * float(second_number))
        
    if math == "division":
        e.insert(0, f_num / float(second_number))

    if math == "modulation":
        e.insert(0, f_num % int(float(second_number)))

   
def button_add():
    first_number = e.get()
    global f_num
    global math
    math = "addition"
    f_num = int(float(first_number))
    e.delete(0, END)

def button_subtract():
    first_number = e.get()
    global f_num
    global math
    math = "subtraction"
    f_num = int(float(first_number))
    e.delete(0, END)

def button_multiply():
    first_number = e.get()
    global f_num
    global math
    math = "multiplication"
    f_num = int(float(first_number))
    e.delete(0, END)

def button_divide():
    first_number = e.get()
    global f_num
    global math
    math = "division"
    f_num = int(float(first_number))
    e.delete(0, END)

def button_modulo():
    first_number = e.get()
    global f_num
    global math
    math = "modulation"
    f_num = int(float(first_number))
    e.delete(0, END)

def button_num(number):
    current=e.get()
    e.delete(0, END)
    e.insert(0,str(current)+ str(number))

def button_decimal():
    current = e.get()
    e.delete(0, END)
    e.insert(0, str(current) + str("."))

    

#Number buttons

button_1 = Button(root, text="1", padx=25, pady=20, command=lambda: button_press(1))
button_2 = Button(root, text="2", padx=25, pady=20, command=lambda: button_press(2))
button_3 = Button(root, text="3", padx=25, pady=20, command=lambda: button_press(3))
button_4 = Button(root, text="4", padx=25, pady=20, command=lambda: button_press(4))
button_5 = Button(root, text="5", padx=25, pady=20, command=lambda: button_press(5))
button_6 = Button(root, text="6", padx=25, pady=20, command=lambda: button_press(6))
button_7 = Button(root, text="7", padx=25, pady=20, command=lambda: button_press(7))
button_8 = Button(root, text="8", padx=25, pady=20, command=lambda: button_press(8))
button_9 = Button(root, text="9", padx=25, pady=20, command=lambda: button_press(9))
button_0 = Button(root, text="0", padx=25, pady=20, command=lambda: button_press(0))

#Function buttons

button_div = Button(root, text="/", padx=26, pady=20, command=button_divide)
button_mult = Button(root, text="*", padx=26, pady=20, command=button_multiply)
button_sub = Button(root, text="-", padx=26, pady=20, command=button_subtract)
button_C = Button(root, text="C", padx=24, pady=20, command=lambda: button_clear())
button_equal = Button(root, text="=", padx=24, pady=20, command=button_equal)
button_add = Button(root, text="+", padx=25, pady=20, command=button_add)
button_dec = Button(root, text=u'\u002E', padx=26, pady=20, command=button_decimal)
#button_lparen = Button(root, text="(", padx=26, pady=20, command=button_lparen)
#button_rparen = Button(root, text=")", padx=26, pady=20, command=button_rparen)
button_mod = Button(root, text="%", padx=24, pady=20, command=button_modulo)

#Frame

button_1.grid(row=3, column=0)
button_2.grid(row=3, column=1)
button_3.grid(row=3, column=2)
button_sub.grid(row=3, column=3)

button_4.grid(row=2, column=0)
button_5.grid(row=2, column=1)
button_6.grid(row=2, column=2)
button_mult.grid(row=2, column=3)

button_7.grid(row=1, column=0)
button_8.grid(row=1, column=1)
button_9.grid(row=1, column=2)
button_div.grid(row=1, column=3)

button_0.grid(row=4, column=0)
button_C.grid(row=4, column=1)
button_equal.grid(row=4, column=2)
button_add.grid(row=4, column=3)

button_dec.grid(row=5, column=0)
#button_lparen.grid(row=5, column=1)
#button_rparen.grid(row=5, column=2)
button_mod.grid(row=5, column=3)