def regex2post(regE):  # Convert regular expression from infix to postfix

    precedenceMap = {
        '(' : 1,
        ')' : 1,
        '?' : 2,
        '*' : 2,
        '+' : 2,
        '.' : 3
    }


    postfix_reg = ''
    operator_stack = Stack()
    print(regE)
    for c in regE:
        if c.isalpha():
            postfix_reg += c
        elif (c == '*' or c == '+' or c == '?' or c == '.' or c == '(') and operator_stack.isEmpty():
            operator_stack.push(c)
        elif (c == '*' or c == '+' or c == '?' or c == '.' or c == '(' or c == ')') and not(operator_stack.isEmpty()):
            previous_operator = operator_stack.pop()
            print(previous_operator)
            if previous_operator != '(' and previous_operator != ')' and precedenceMap[previous_operator] >= precedenceMap[c]:
                postfix_reg += previous_operator
                operator_stack.push(c)
            if previous_operator == '(':
                operator_stack.push(previous_operator)
                operator_stack.push(c)
            if c == ')':
                previous_operator = operator_stack.pop()
                while not (previous_operator == '('):
                    postfix_reg += previous_operator
                    previous_operator = operator_stack.pop()

    while not(operator_stack.isEmpty()):
        postfix_reg += operator_stack.pop()

    return postfix_reg