该程序提供商品，让用户为商品付款，“给予”商品并更新每个商品的库存。它似乎或多或少地起作用。我有两个问题：
1）在用户回答“ n”以“购买其他商品”后，我不知道如何退出自动售货机程序？ （y / n）：“。
2）有没有办法使代码更简单/更好？
def vend():
a = {'item': 'choc', 'price': 1.5, 'stock': 2}
b = {'item': 'pop', 'price': 1.75, 'stock': 1}
c = {'item': 'chips', 'price': 2.0, 'stock': 3}
d = {'item': 'gum', 'price': 0.50, 'stock': 1}
e = {'item': 'mints', 'price': 0.75, 'stock': 3}
items = [a, b, c, d, e]
cim = 0 # cash in machine
print('welcome to vending machine! \n***************')
# show items, prices
def show(items):
print('\nitems available \n***************')
for item in items:
if item.get('stock') == 0:
items.remove(item)
for item in items:
print(item.get('item'), item.get('price'))
print('***************\n')
# have user choose item
while True:
show(items)
selected = input('select item: ')
for item in items:
if selected == item.get('item'):
selected = item
price = selected.get('price')
while cim < price:
cim = float(input('insert ' + str(price - cim) + ': '))
else:
print('you got ' + selected.get('item'))
selected['stock'] -= 1
cim -= price
print('cash remaining: ' + str(cim))
a = input('buy something else? (y/n): ')
if a == 'n':
if cim != 0:
print(str(cim) + ' refunded')
cim = 0
print('thank you, have a nice day!\n')
break
else:
print('thank you, have a nice day!\n')
break
else:
continue
vend()
答案 0 :(得分：1)
1）我不知道如何在退出自动售货机程序后 用户回答“ n”以“购买其他东西？ （y / n）：“。
Python中的 break 语句从封闭它的第一个 for 或 while 循环中跳出。您只退出显示的 for 循环。 while为真的条件使您永远循环播放。
但是，您做得很聪明，将所有自动售货机功能都包含在 vend 功能中。如果使用 return 语句代替 break ，则不仅会退出 vend 功能，还会到达整个程序的结尾然后根据需要退出。
return 语句还用于从函数调用中返回值，但是在这种情况下您不需要这样做。
此外，您不需要，也不应该具有该函数的两个单独的出口。删除以下三行：
else:
print('thank you, have a nice day!\n')
break
在您删除的三行上方紧缩两行，然后将 break 替换为 return 。
您还可以进行其他改进，但这只是一个开始。
答案 1 :(得分：1)
您只需要添加一个布尔变量，如果用户的答案是n，则将其设置为false。另请注意，代码中存在问题，您没有以正确的方式更新cim的值。您必须考虑一个人可能需要输入多个硬币，因此您必须累计插入的硬币总数：
def vend():
a = {'item': 'choc', 'price': 1.5, 'stock': 2}
b = {'item': 'pop', 'price': 1.75, 'stock': 1}
c = {'item': 'chips', 'price': 2.0, 'stock': 3}
d = {'item': 'gum', 'price': 0.50, 'stock': 1}
e = {'item': 'mints', 'price': 0.75, 'stock': 3}
items = [a, b, c, d, e]
cim = 0 # cash in machine
print('welcome to vending machine! \n***************')
# show items, prices
def show(items):
print('\nitems available \n***************')
for item in items:
if item.get('stock') == 0:
items.remove(item)
for item in items:
print(item.get('item'), item.get('price'))
print('***************\n')
continueToBuy = True
# have user choose item
while continueToBuy == True:
show(items)
selected = input('select item: ')
for item in items:
if selected == item.get('item'):
selected = item
price = selected.get('price')
while cim < price:
cim = cim + float(input('insert ' + str(price - cim) + ': '))
print('you got ' + selected.get('item'))
selected['stock'] -= 1
cim -= price
print('cash remaining: ' + str(cim))
a = input('buy something else? (y/n): ')
if a == 'n':
continueToBuy = False
if cim != 0:
print(str(cim) + ' refunded')
cim = 0
print('thank you, have a nice day!\n')
break
else:
print('thank you, have a nice day!\n')
break
else:
continue
vend()
此外，我认为这是介绍面向对象编程的一个很好的例子。它允许您拥有更好的结构化代码，并使您专注于想要开发的逻辑。这是一个可能的实现：
class Item:
def __init__(self, name, price, stock):
self.name = name
self.price = price
self.stock = stock
def updateStock(self, stock):
self.stock = stock
def buyFromStock(self):
if self.stock == 0:
# raise not item exception
pass
self.stock -= 1
class VendingMachine:
def __init__(self):
self.amount = 0
self.items = []
def addItem(self, item):
self.items.append(item)
def showItems(self):
print('\nitems available \n***************')
for item in self.items:
if item.stock == 0:
self.items.remove(item)
for item in self.items:
print(item.name, item.price)
print('***************\n')
def addCash(self, money):
self.amount = self.amount + money
def buyItem(self, item):
if self.amount < item.price:
print('You can\'t but this item. Insert more coins.')
else:
self.amount -= item.price
item.buyFromStock()
print('You got ' +item.name)
print('Cash remaining: ' + str(self.amount))
def containsItem(self, wanted):
ret = False
for item in self.items:
if item.name == wanted:
ret = True
break
return ret
def getItem(self, wanted):
ret = None
for item in self.items:
if item.name == wanted:
ret = item
break
return ret
def insertAmountForItem(self, item):
price = item.price
while self.amount < price:
self.amount = self.amount + float(input('insert ' + str(price - self.amount) + ': '))
def checkRefund(self):
if self.amount > 0:
print(self.amount + " refunded.")
self.amount = 0
print('Thank you, have a nice day!\n')
def vend():
machine = VendingMachine()
item1 = Item('choc', 1.5, 2)
item2 = Item('pop', 1.75, 1)
item3 = Item('chips', 2.0, 3)
item4 = Item('gum', 0.50, 1)
item5 = Item('mints',0.75, 3)
machine.addItem(item1)
machine.addItem(item2)
machine.addItem(item3)
machine.addItem(item4)
machine.addItem(item5)
print('Welcome to the vending machine!\n***************')
continueToBuy = True
while continueToBuy == True:
machine.showItems()
selected = input('select item: ')
if machine.containsItem(selected):
item = machine.getItem(selected)
machine.insertAmountForItem(item)
machine.buyItem(item)
a = input('buy something else? (y/n): ')
if a == 'n':
continueToBuy = False
machine.checkRefund()
else:
continue
else:
print('Item not available. Select another item.')
continue
vend()
有关OOP的更多信息，请参见a resource like this。