# Vending Machine Model Assignment Solutions

July 08, 2024
Prof. Dominic
🇬🇧 United Kingdom
Programming
Prof. Dominic Walton, an esteemed programming exam taker, hails from the University of Glasgow, UK. With a distinguished 15-year tenure and a Ph.D. under his belt, his expertise ensures unparalleled excellence in exam execution.
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Implement a class that models a vending machine.

The vending machines we model shall be quite simple. They hold a single kind of drink, assume a bottle of water. They can accept money (the US, coins, but not pennies) and can dispense drinks and return change.

Solution:

```# File: VendingMachine.py # # Create a class that models a vending machine. # # # Name: # EID: # Email: # Grader: # # On my honor, , this programming assignment is my own work # and I have not provided this code to any other student. import random # CS303e Students. Complete the VendingMachine class below as # specified in the assignment handout. Delete this comment afterwards. """Models a Vending Machine. All transactions are in cents. """ class VendingMachine: def __init__(self, numDrinks, price: int, capacity): if numDrinks > capacity: raise KeyError() if price <= 0: raise KeyError() self.capacity = capacity self.price = price self.money: int = 0 self.numDrinks = numDrinks def insert_money(self, money): self.money += money def can_dispense(self): return self.numDrinks > 0 and self.money >= self.price def dispense(self): if self.numDrinks <= 0: return 'EMPTY' elif self.money < self.price: return 'INSUFFICIENT FUNDS' else: self.money = self.money - self.price self.numDrinks -= 1 return 'ENJOY' def get_change(self): money = self.money self.money = 0 return money def refill(self): self.numDrinks = self.capacity def main(): """# Run a simulation using the Vending Machine objects.""" if input('Run simple tests? ') == 'y': simple_tests() stress_tests() def simple_tests(): """Simple operations with a single Vending Machine. The VendingMachine has a capacity of 5 drinks, currently has 2 drinks, and it costs 50 cents per drink. """ print('***** SIMPLE TESTS *****') vend1 = VendingMachine(2, 50, 5) vend1.insert_money(25) vend1.insert_money(10) vend1.insert_money(10) print('can dispense:', vend1.can_dispense()) print('dispense:', vend1.dispense()) vend1.insert_money(10) print('can dispense:', vend1.can_dispense()) print('dispense:', vend1.dispense()) print('can dispense:', vend1.can_dispense()) print('get change:', vend1.get_change()) print('get change:', vend1.get_change()) vend1.insert_money(100) vend1.insert_money(25) print('can dispense:', vend1.can_dispense()) print('dispense:', vend1.dispense()) print('can dispense:', vend1.can_dispense()) print('dispense:', vend1.dispense()) vend1.refill() print('can dispense:', vend1.can_dispense()) print('dispense:', vend1.dispense()) print('can dispense:', vend1.can_dispense()) print('dispense:', vend1.dispense()) print('get change:', vend1.get_change()) print() def stress_tests(): """Run stress tests. Given the same number of machines, the same number of operations, and the same initial seed, output will be the same. """ # Get the seed, number of operations, # and number of machines from the user. random.seed(int(input('Enter random seed: '))) num_operations = int(input('Enter the number of operations: ')) num_machines = int(input('Enter the number of machines: ')) print('\n***** STRESS TESTS *****') # Create the required number of machines and run the tests. machines = create_machines(num_machines, 10) perform_stress_tests_ops(machines, num_operations) def perform_stress_tests_ops(machines, num_operations): """# Run the actual operations for the stress tests.""" # Only allow US coins, excluding pennies! # (We should get rid of pennies and probably nickels too!) coins = [5, 10, 25, 50, 100] last_coin_index = len(coins) - 1 last_machine_index = len(machines) - 1 # Pick a random operation. # 55% chance of insert_money. # 20% chance of can dispense. # 21% chance of dispense. (If we dispense, there is a 80% # chance dispense is called directly after.) # 3% chance of get_change. # 1% chance of refill. for i in range(1, num_operations + 1): print('Operation =', i) machine_number = random.randint(0, last_machine_index) print('Machine =', machine_number) machine = machines[machine_number] random_op = random.randint(1, 100) if random_op <= 55: coin = coins[random.randint(0, last_coin_index)] print('Insert money, amount =', coin) machine.insert_money(coin) elif random_op <= 75: print('Can dispense:', machine.can_dispense()) elif random_op <= 96: result = machine.dispense() print('Dispense:', result) if result == 'ENJOY': # Do they remember their change? 80% chance of yes. if random.randint(1, 5) <= 4: print('Get change, amount =', machine.get_change()) else: print('Forgot change after dispense.') elif random_op <= 99: print('Get change, amount =', machine.get_change()) else: print('Refill.') machine.refill() print() def create_machines(num_machines, max_capacity): """Create a list with the required number of machines. I expect num_machines > 0. The first machine always has a price of 25, 1 drink, and a capacity of 3. All machines will have a price between 25 and 200 in multiples of 25. All machines will have a capacity between 2 and max_capacity. """ price_multiplier = 25 machines = [VendingMachine(1, price_multiplier, 3)] print('Machine 0: price = 25, capacity = 3, initial drinks = 1') for i in range(1, num_machines): price = random.randint(1, 8) * price_multiplier capacity = random.randint(2, max_capacity) drinks = random.randint(0, capacity) print('Machine ', i, ': price = ', price, ', capacity = ', capacity, ', initial drinks = ', drinks, sep='') machines.append(VendingMachine(drinks, price, capacity)) print() return machines main() ```

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