Your task is to implement a simplified prefix calculator in Python.

An expression is written in prefix notation when the operator is written before the operands.

Your calculator will accept and evaluate expressions that contain a single operator followed by an arbitrary number of operands. Operands may be integers or floating point numbers, separated by an arbitrary number of space characters.

The operators are: + (for addition), - (for subtraction), * (for multiplication) and / (for division).

Your calculator must also accept and ignore input that starts with # (comments).

The program must exit when the user enters 'q'.

The starter file provided includes support for addition and simple error handling. Your task is to add support for -, *, / and #.

For example:

+ 5 3 2 1 is (5 + 3 + 2 + 1)

* 3 4 2 is (3 * 4 * 2)

/ 100 5 4 2 is (((100 / 5) / 4) / 2)

- 1 10 2 3 is (((1 - 10) -2) - 3)

Make sure you read and follow the grading rubric provided. Note that your implementation must reuse the functions and data structures provided in the starter file calculator.py.

Here is a sample run:

CS 152 >>>+ 10 20

30

CS 152 >>>+ 5 3 2 1

11

CS 152 >>>* 2 3.1

6.2

CS 152 >>>* 3 4 2

24

CS 152 >>>* 1 2 3 4 5 6

720

CS 152 >>>- 10 2.5

7.5

CS 152 >>>- 1 10 2 3

-14

CS 152 >>>/ 100 5

20.0

CS 152 >>>/ 100 5 4

5.0

CS 152 >>># this is just a comment

CS 152 >>>

CS 152 >>>89

Error: expected # or * or + or - or /, got 89

Please enter a valid expression in prefix notation or q to quit

CS 152 >>>& 3 4 5

Error: expected # or * or + or - or /, got &

Please enter a valid expression in prefix notation or q to quit

CS 152 >>>9 + 2

Error: expected # or * or + or - or /, got 9

Please enter a valid expression in prefix notation or q to quit

CS 152 >>>

CS 152 >>>+

0

CS 152 >>>-

0

CS 152 >>>/

0

CS 152 >>>*

0

CS 152 >>>#

CS 152 >>>+ 7

7

CS 152 >>>- 9

9

CS 152 >>>* 4

4

CS 152 >>>/ 8

8

CS 152 >>>/ 8 0

Error: expected non zero operand, got 0

Please enter a valid expression in prefix notation or q to quit

CS 152 >>>/ 8 4 0 2

Error: expected non zero operand, got 0

Please enter a valid expression in prefix notation or q to quit

CS 152 >>>q

Exiting the CS 152 Calculator

Calculator.py:

def add(operands):  result = 0 for each_operand in operands: each_value = get_value(each_operand)   if each_value is not None:   result += each_value else:   return  return result # Return the sum.  SUPPORTED_OPERATORS = {'+': add} SUPPORTED_SYMBOLS = sorted(SUPPORTED_OPERATORS.keys()) 

def subtract():

def divide():

def multiply():

ef evaluate(expression):   if not expression: return  result = None    tokens = expression.split() operator = tokens[0]   operands = tokens[1:] if operator in SUPPORTED_OPERATORS: function_name = SUPPORTED_OPERATORS[operator] result = function_name(operands) else: expected_operators = ' or '.join(SUPPORTED_SYMBOLS) error(expected_operators, operator) if result is not None: print(result) def get_value(a_string):   try:  value = int(a_string) except ValueError:   try:  value = float(a_string) except ValueError: error('number', a_string) return  return value def error(expected, error):   print("Error: expected {}, got {}".format(expected, error)) print('Please enter a valid expression in prefix notation or q to quit') def main(): more_input = True  while more_input: expression = input("CS 152 >>>") if expression == 'q': more_input = False  print('Exiting the CS 152 Calculator') else: evaluate(expression) if __name__ == '__main__': main()