main.py

from tkinter import*
import _ast

root = Tk()
root.title("Calculator")
#get the user to input
i = 0
def get_variables(num):
    global i
    display.insert(i,num)
    i+=1

def calculator():
    entire_string = display.get()
    try:
        result = eval(entire_string)
        clear_all()
        display.insert(0,result)
    except Exception:
        clear_all()
        display.insert(0,"Error")

def get_operator(operator):
    global i
    length = len(operator)
    display.insert(i,operator)
    i+=length

def factorial(num):
    if num == 1:
        return 1
    else:
        return num*factorial(num - 1)

def clear_all():
    display.delete(0,END)

def undo():
    entire_string = display.get()
    if len(entire_string):
        new_string = entire_string[:-1]
        clear_all()
        display.insert(0,new_string)
    else:
        clear_all()
        display.insert(0,"Error")
#adding the input field
display = Entry(root)
display.grid(row=1,columnspan=6,sticky=W+E)

#adding buttons to the calculator
Button(root, text="1", command = lambda: get_variables(1)).grid(row=2,column=0)
Button(root, text="2", command = lambda: get_variables(2)).grid(row=2,column=1)
Button(root, text="3", command = lambda: get_variables(3)).grid(row=2,column=2)
Button(root, text="4", command = lambda: get_variables(4)).grid(row=3,column=0)
Button(root, text="5", command = lambda: get_variables(5)).grid(row=3,column=1)
Button(root, text="6", command = lambda: get_variables(6)).grid(row=3,column=2)
Button(root, text="7", command = lambda: get_variables(7)).grid(row=4,column=0)
Button(root, text="8", command = lambda: get_variables(8)).grid(row=4,column=1)
Button(root, text="9", command = lambda: get_variables(9)).grid(row=4,column=2)

#adding other buttons to the calculator
Button(root,text="AC",command = lambda: clear_all()).grid(row=5,column=0)
Button(root,text="0", command = lambda: get_variables(0)).grid(row=5,column=1)
Button(root,text="=",command = lambda: calculator()).grid(row=5,column=2)

Button(root,text="+",command= lambda: get_operator("+")).grid(row=2,column=3)
Button(root,text="-",command= lambda: get_operator("-")).grid(row=3,column=3)
Button(root,text="*",command= lambda: get_operator("*")).grid(row=4,column=3)
Button(root,text="/",command= lambda: get_operator("/")).grid(row=5,column=3)

#adding new operations
Button(root,text="pi",command= lambda: get_operator("3.1415926")).grid(row=2,column=4)
Button(root,text="%",command= lambda: get_operator("%")).grid(row=3,column=4)
Button(root,text="(",command= lambda: get_operator("(")).grid(row=4,column=4)
Button(root,text="exp",command= lambda: get_operator("**")).grid(row=5,column=4)

Button(root,text="<-",command= lambda: undo()).grid(row=2,column=5)
Button(root,text="x!",command= lambda: get_operator("!")).grid(row=3,column=5)
Button(root,text=")",command= lambda: get_operator(")")).grid(row=4,column=5)
Button(root,text="^2",command= lambda: get_operator("**2")).grid(row=5,column=5)




root.mainloop()