爲什麼for循環返回None？

我正在從Code Academy進行練習以遍歷shopping_list。爲什麼下面的代碼結果在結果中返回一個額外的None？爲什麼for循環返回None？

shopping_list = ["banana","apple"] 

stock = { "banana": 6, 
    "apple": 0, 
    "orange": 32, 
    "pear": 15 
} 

prices = { "banana": 4, 
    "apple": 2, 
    "orange": 1.5, 
    "pear": 3 
} 

# Write your code below! 
def compute_bill(food): 
    total = 0 
    for x in food: 
     print x 
     total += prices[x] 
compute_bill(shopping_list)

來源

2013-10-08 phill

你的函數將返回'None'。也許你的環境只是在函數運行後顯示返回值 –

＃在下面寫下你的代碼！ DEF compute_bill（食品）：總= 0 用於食品中X：打印X 總+ =價格[X] 返回總打印「總：」 + STR（compute_bill（和shopping_list）） – ChuckCottrill

第二示例後本教程的這一部分 - 。 – wwii

shopping_list = ["banana","apple"] 

stock = { "banana": 6, 
    "apple": 0, 
    "orange": 32, 
    "pear": 15 
} 

prices = { "banana": 4, 
    "apple": 2, 
    "orange": 1.5, 
    "pear": 3 
} 

# Write your code below! 
def compute_bill(food): 
    total = 0 
    for x in food: 
     print x 
     total += prices[x] 
    return total 
print(compute_bill(shopping_list))

您需要使用return語句獲取功能compute_bill的結果。

來源

2013-10-08 04:38:10 YaleCheung

爲什麼for循環返回None？

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