Entry Tkinter

from tkinter import *
from math import *
from numpy import *
root = Tk()
e1=Entry()
e2=Entry()
e3=Entry()
e4=Entry()
a=e1.get()
b=e2.get()
n=e3.get()
 
 
inp=e4.get()
def f(x): 
    return eval(inp)
 
 
def simpson(a, b, n):
    if (int(n) % 2 != 0):
        n += 1
    k = int(n) / 2
    h = (int(b) - int(a)) / int(n)
    h2 = h * 2
    S = (f(a) + f(b)) / 2
    x = h
    k = int(k)
    for i in range(0, k - 1):
        S += 2 * (f(x))
        S += f(x + h)
        x += h2
    S += 2 * (f(x))
    S *= h * 2 / 3
    return S
 
print(simpson(a,b,n))
 
def button_clicked():
    print(simpson_rule(a,b,n))
 
 
button = Button(root)
button.configure(text="vichislit",command=button_clicked)
e1.pack()
e2.pack()
e3.pack()
e4.pack()
button.pack()
root.mainloop()

from tkinter import *
from math import *
from numpy import *
root = Tk()
e1=Entry()
e2=Entry()
e3=Entry()
e4=Entry()
a=e1.get()
b=e2.get()
n=e3.get()
inp=e4.get()
def f(x):
    return eval(inp)
def simpson_rule(f, a, b, n):
    a=int(e1.get())
    b=int(e2.get())
    n=int(e3.get())
    if (n % 2 != 0):
        n += 1
    k = n / 2
    h = (b - a) / n
    h2 = h * 2
    S = (f(a) + f(b)) / 2
    x = h
    k = int(k)
    for i in range(0, k - 1):
        S += 2 * (f(x))
        S += f(x + h)
        x += h2    
    S += 2 * (f(x))
    S *= h * 2 / 3
    return S
def button_clicked():
    print(simpson_rule(a,b,n,f))
button = Button(root)
button.configure(text="vichislit",command=button_clicked)
e1.pack()
e2.pack()
e3.pack()
e4.pack()
button.pack()
root.mainloop()