import re while True: input_data = input() operators = ['+', '-', '*', '/'] if input_data.strip() == 'q': break l_task = [i.strip() for i in re.split("(\d+\.*\d*)", input_data) if i != ''] print(l_task) for i, v in enumerate(l_task): if i % 2 == 0 and not isinstance(float(v), float): print("Операнд %d не является числом" % ((i + 2) / 2)) if i % 2 != 0 and v not in operators: print("Введён некорректный оператор %d" % ((i + 1) / 2)) res = float(l_task[0]); for i in range(1, len(l_task), 2): if l_task[i] == operators[0]: res += float(l_task[i+1]) elif l_task[i] == operators[1]: res -= float(l_task[i+1]) elif l_task[i] == operators[2]: res *= float(l_task[i+1]) elif l_task[i] == operators[2]: res /= float(l_task[i+1]) print("%.4f" % res)