Vending Machine

import ast
import sys

class Vending_Machine:
    def __init__(self, products, change):
        self.products = products
        self.change = change

    def reset_products(self):
        print("Let's reload the products")
        products = ast.literal_eval(input("Enter a dictionary with the product name as key and its price as the value. eg {\"Coke\": 0.5, \"iPhone\":600}\n"))
        self.products = products
        print("The products have been reset, you may now continue using the Vending Machine")

    def reset_change(self):
        print("Let's now reload the change")
        change = ast.literal_eval(input("Enter a dictionary with the coin denomination as key and its quantity as the value. eg {\"0.01\": 5, \"2\":20}\n"))
        self.change = change
        print("The change has been reset, you may now continue using the Vending Machine")

    def buy_product(self, productName):
        if productName in self.products:
            amount = input("How much are you paying for it?\n")
            change = round((float(amount) - self.products[productName])*100)
            if change < 0:
                print("Insufficient Funds")
                return
            elif change == 0:
                print("Here's your %s, thanks for providing the exact amount!" % productName)
            else:
                original_vals = [i for i in self.change.keys()]
                vals = [round(float(i)*100) for i in self.change.keys()]      #converting all denomination to pennies
                amts = [i for i in self.change.values()]      #the amount of each denomination
                best = [[0 for i in vals]]      #memo for dynamic programming
                bestScoreList = [0]
                for i in range(1, change+1):
                    best.append([0]*len(vals))
                    bestScore = i+1
                    for c in range(len(vals)):
                        if vals[c] > i or best[i - vals[c]][c] >= amts[c]:
                            continue
                        bestIndex = i - vals[c]
                        score = 0
                        if bestScoreList[bestIndex] != 0 or bestIndex == 0:
                            score = bestScoreList[bestIndex] + 1
                        if score < bestScore:
                            bestScore = score
                            best[i] = list(best[bestIndex])
                            best[i][c] += 1
                    bestScoreList.append(bestScore)

                #best[change] will be in a form like [0, 3, 2] which means 3 unit of the denomination at vals[1] and 2 units of denomination at vals[2]
                #here we check if Vending Machine can't give that change (the denominations in best[change] will not add up to the change)
                sum = 0
                for ind, k in enumerate(best[change]):
                    change_key = vals[ind]
                    sum += change_key * k

                if sum < change:
                    print("Sorry, I don't have change for that. Please try buying with a different amount")
                    return

                returned_change = dict()

                #here we convert the best[change] into a dictionary showing the amount of each denomination
                #simultaneously we are also removing the amount of each denomination from the the change contained in the Vending Machine
                for ind, k in enumerate(best[change]):
                    if k != 0:
                        change_key = original_vals[ind]
                        returned_change[change_key] = k
                        frequency = self.change[change_key]
                        frequency -= k
                        if frequency == 0:
                            self.change.pop(change_key, None)
                        else:
                            self.change[change_key] = frequency

                print("Here's your change")
                print(returned_change)

            self.products.pop(productName, None)
        else:
            print("Invalid product name")

    def get_products(self):
        for product, price in self.products.items():
            print("%s %s" % (product, price))


def executeCommand(vm, command, parameter):
    if command == "help":
        print("Commands Manual")
        print("<...> is just a placeholder")
        print("reset_products - to reset the products in the vending machine")
        print("reset_change - to reset the change in the vending machine")
        print("buy <item name> - to buy the specified item")
        print("see - to view all the items you can buy")
        print("quit - to finish the game")

    elif command == "see":
        vm.get_products()

    elif command == "reset_products":
        vm.reset_products()

    elif command == "reset_change":
        vm.reset_change()

    elif command == "buy":
        vm.buy_product(parameter)

    elif command == "quit":
        sys.exit("Thanks for playing! Hope you enjoyed the game")

    else:
        print("Invalid command, type help for list of commands")


def main():
    print("Vending Machine 1.0")
    print("Let's load the products")
    products = ast.literal_eval(input("Enter a dictionary with the product name as key and its price as the value. eg {\"Coke\": 0.5, \"Pen\":6}\n"))
    print("Let's now set the change")
    change = ast.literal_eval(input("Enter a dictionary with the coin denomination (to two decimal place) as key and its quantity as the value. eg {\"0.01\": 5, \"2.00\":20}\n"))

    vm = Vending_Machine(products, change)

    print("Great, now you can interact with the vending machine")
    print("Try typing \'help\' to see a list of commands")

    while(True):
        user_input = input()
        input_list = user_input.split(" ")
        command = input_list[0]
        parameter = "no parameter"
        if len(input_list) > 1:
            parameter = " ".join(input_list[1:])
        print()
        executeCommand(vm, command, parameter)
        print()

main()