def calculateMolecularWeight() :
    Compound = userinput.get()
    tokens = re.findall(r'[A-Z][a-z]*|\d+|\(|\)', Compound)
    displayNoOfElements(tokens)
    lblTotal = tk.Label(root, text = ' The Molar mass: ' + str(Compound) + ' is ' + str(round(parse(tokens, []),4)) + ' g/mol .').grid(row = 4, column = 1, padx = 0,pady = 10)
    print(mylist)
    mylist.clear()