#import re module to work with regular expressions
import re

run = True
oldEq = 0

#this is our main function that does all the calculation
def calc():
    #we use global keyword to access the global variables which are declared outside the function
    global run, oldEq
    #we use to variables oldEq and newEq to be able to use the results we get as an expression for the next eval() execution
    if oldEq == 0:
        newEq = input("enter the equation\n")
    else:
        newEq = input(str(oldEq))
    if newEq == 'quit':
        run = False
    else:
        #this remove all letters and punctuations specified in our pattern and make our expression composed of only numbers
        newEq = re.sub('[a-zA-Z,./" "]', '', newEq)
        if oldEq == 0:
            oldEq = eval(newEq)
        else:
            oldEq = eval(str(oldEq) + newEq)
        print("=", oldEq)
#this will check if the run variable is set to True to continue calculating or stop the program incase of run = False
while run:
    calc()