打印添加到列表的最后一項

Question

Okey，所以即時通訊學習python並嘗試建立這個基本的自選游戲...

import random
global gold
gold = 0

class Fruit:
    def __str__(self):
        return self.name

    def __repr__(self):
        return self.name

class Apple(Fruit):
    def __init__(self):
        self.name = "Apple"
        self.desc = "An Red Apple!"
        self.value = "2 Gold"

class Grapes(Fruit):
    def __init__(self):
        self.name = "Grapes"
        self.desc = "Big Green Grapes!"
        self.value = "4 Gold"

class Banana(Fruit):
    def __init__(self):
        self.name = "Banana"
        self.desc = "Long, Fat Yellow Bananas"
        self.value = "5 Gold"

class Orange(Fruit):
    def __init__(self):
        self.name = "Orange"
        self.desc = "Big Orange Orange"
        self.value = "7 Gold"


inventory = []

print ("Fruits!")
print ("To see your inventroy press: i")
print ("To sell fruits press: s")
print ("To pick fruits press: p")

def action():
    return input("Action: ")


def i ():
    print ("Your Inventory: ")
    print ("*" + str(inventory))

def p ():
    pick = [Apple(), Orange(), Grapes(), Banana()]
    inventory.append (random.choice(pick))

def s ():
    print ("...")

while True:
    actioninput = action()
    if actioninput in ["i", "İ"]:
        i ()
    elif actioninput in ["s", "S"]:
        s ()
    elif actioninput in ["p", "P"]:
        p ()
    else:
        print ("Invalid Action!")

所以我的問題是：

1. 在def p（）：中，我要打印已添加到列表中的項目。 我嘗試了一些東西，但是沒有用...

2. 我不知道如何執行“出售”功能，如何從列表中刪除某項並將其值添加到全球黃金中？

我編輯了def s（）：像這樣，我得到一個錯誤：

def s():
    global gold
    sell = input ("What item would you like to sell?")
    if sell == "Apple":
        inventory.remove (Apple)
        gold = gold + 2
    elif sell == "Orange":
        inventory.remove (Orange)
        gold = gold + 7
    elif sell == "Banana":
        inventory.remove (Banana)
        gold = gold + 4
    elif sell == "Grapes":
        inventory.remove (Grapes)
        gold = gold + 5

ValueError: list.remove(x): x not in list

Answer 1

1. “在def p(): ，我要打印已添加到列表中的項目。”

最簡單的方法是只使用一個中間變量：

def p ():
    pick = [Apple(), Orange(), Grapes(), Banana()]
    fruit_picked = random.choice(pick)
    inventory.append (fruit_picked)
    print("you picked a", fruit_picked)

您還可以使用索引[-1]獲得列表的最后一個元素：

def p ():
    pick = [Apple(), Orange(), Grapes(), Banana()]
    inventory.append (random.choice(pick))
    print("you picked a", inventory[-1])

2. “如何從列表中刪除項目並將其值添加到全球黃金中？”

使用list.pop彈出一個項目，然后對它的.value屬性進行處理：

def s():
    global gold #need this in the function that you are modifying the global value
    fruit_sold = inventory.pop() #pop the last item
    gold += fruit_sold.value

3. “如何選擇要從列表中刪除的特定元素”

為此，有幾種方法，無需對您的Fruit類進行修改，您可以遍歷列表並檢查與輸入名稱相同的水果：

def s():
    global gold
    fruit_to_sell = input("what kind of fruit do you want to sell? ")
    for fruit in inventory:
        if fruit.name == fruit_to_sell:
            gold+=fruit.value
            inventory.remove(fruit)
            print("ok, you just sold a(n) {0} for {0.value} gold".format(fruit))
            return #finish the function
    #if no fruit was found
    print("you don't have any of those kind of fruit \n" + 
          "(This demo doesn't check for capitalization)")

出現錯誤的原因是因為您試圖從清單中刪除該類 ，所以列表中僅存在Fruit對象，因此沒有任何意義：

Apple == Apple() #almost always false, unless you   specifically overloaded __eq__ to make it True.

您可以對Fruit類進行更改，以便只要這些水果是同一類型（子類），它們的比較結果就相等：

class Fruit:
    def __eq__(self,other):
        return type(self) == type(other) 
    ...

那么您只需稍微調整一下賣出即可刪除任何實例：

def s():
    global gold
    sell = input ("What item would you like to sell?")
    if sell == "Apple":
        inventory.remove (Apple()) #make an instance here@
        gold = gold + 2
    elif sell == "Orange":
        inventory.remove (Orange())
        ... #you get the point

雖然如果您嘗試在沒有蘋果的情況下嘗試出售蘋果，這仍然會引發錯誤，但最好檢查一下是否有第一個蘋果：

def s():
    global gold
    sell = input ("What item would you like to sell?")
    if sell == "Apple":
        selling = Apple()
    elif sell == "Orange":
        selling = Orange()
    elif sell == "Banana":
        selling = Banana()
    elif sell == "Grapes":
        selling = Grapes()
    if selling in inventory: #make sure you have some of what ever you are selling before trying to sell it!
        inventory.remove(selling)
        gold += int(selling.value.rstrip(" Gold"))
         # I didn't realize value was a str, this shoddy conversion
         #  works but is not a very good solution
    else:
        print("you don't have any of those!\n"+
              "(This demo doesn't check for capitalization)")

Answer 2

使用isinstance（）來檢測對象屬於哪個類。

保持全局變量不是一個好方法。 也許開始建立一個值以將功能作為一個帳戶傳遞出去。

然后在購買前檢查余額。 （預算外）等

Answer 3

list_name[-1]是列表中的最后一項，因此是最近添加的一項。

在您的情況下：廣告inventory[-1]

在賣方功能中，您可以使用list_name.remove('element_to_be_removed')刪除列表中的元素。

在您的情況下：

fruit_to_remove = inventory[-1]
inventory.remove(fruit_to_remove)

或使用list.pop() 。 （根據Tadhg McDonald-Jensen的評論）