Exercise 7.3 (rpn_calculator.py). Write a reverse Polish notation calculator. In reverse Polish notation (also known as HP calcula- tor notation), mathematical expressions are written with the operator following its operands. For example, 3 +4 becomes 3 4+. Order of operations is entirely based on the ordering of the operators and operands. To write 3 +(4*2), we would write 42 3 + in RPN. The expressions are evaluated from left to right. A longer example of an expression is this: 512/43- which translates to If you were to try to "parse" the RPN expression from left to right, you would probably remember" values until you hit an operator, at which point you take the last two values and use the operator on them. In the example expression above, you would store 5, then 1, then 2, then see the division operator (/) and take the last two values you stored (1 and 2) to do the division. Then, you would store the result of that (0.5) and encounter 4, which you store. When you encounter the multiplication sign (), you would take the last two values stored and do the operation (4 0.5) and store that. Following this through step by step, the steps would look something like this (the bold number is the most recently computed value): Exercise 7.3 (rpn_calculator.py). Write a reverse Polish notation calculator. In reverse Polish notation (also known as HP calcula- tor notation), mathematical expressions are written with the operator following its operands. For example, 3 +4 becomes 3 4+. Order of operations is entirely based on the ordering of the operators and operands. To write 3 +(4*2), we would write 42 3 + in RPN. The expressions are evaluated from left to right. A longer example of an expression is this: 512/43- which translates to If you were to try to "parse" the RPN expression from left to right, you would probably remember" values until you hit an operator, at which point you take the last two values and use the operator on them. In the example expression above, you would store 5, then 1, then 2, then see the division operator (/) and take the last two values you stored (1 and 2) to do the division. Then, you would store the result of that (0.5) and encounter 4, which you store. When you encounter the multiplication sign (), you would take the last two values stored and do the operation (4 0.5) and store that. Following this through step by step, the steps would look something like this (the bold number is the most recently computed value)