Lab-1

while True:
    print("Write infix notated expression or '-exit': ")
    line = input()

    def Tokenize(line):
        numbers_buffer = []
        tokens = []
        for s in line:

            if s.isdigit():
                numbers_buffer.append(s)

            elif s == "+" or s == "-" or s == "*" or s =="/" or s == "(" or s ==')' or s == "":
                if len(numbers_buffer) != 0:
                    token = ""
                    for i in numbers_buffer:
                        token += i
                        numbers_buffer.clear()
                        tokens.append(token)
                if s != '':
                   tokens.append(s)
        print(tokens)

        return tokens

    def InfixToPostfix(tokens):
        postFix = ''
        s = []
        for c in tokens:
            if c in "123456789":
             postFix += c
            elif c in "+-":
                if len(s) == 0:
                    s.append(c)
                elif s[0] == '(':
                    s.append(c)
            elif c in "*/":
               if len(s) == 0:
                   s.append(c)
               elif s[0] in "+-(":
                 s.append(c)
            elif c == "(":
                s.append(c)
            elif c == ")":
                postFix += s.pop()
                s.pop()
            else:
                print("Error")

        print(postFix)
        return postFix

    def CalsulatePostfix(postfix):
        print("")

    if line == '-exit':
        break
    else:
        infixTokens = Tokenize(line)
        postfixTokens = InfixToPostfix(infixTokens)
        result = CalsulatePostfix(postfixTokens)